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Retaining Rings


  • Allow Easy Mounting of Optical Components
  • Compatible with Our Line of Lens Tubes and Mounts
  • Extra-Thick, Stress-Free, Delrin (Plastic), and Stainless Steel Versions
  • M5.5 x 0.5 to SM4 Threading

CMRR

C-Mount (1.00"-32) Retaining Ring

SM05LTRR

SM05 (0.535"-40)
Stress-Free Retaining Ring

SM1PRR

SM1 (1.035"-40)
Plastic Retaining Ring

SM75RR

SM75 (M75.5 x 0.5)
Retaining Ring

SM4RR

SM4 (4.035"-40)
Retaining Ring

SM2RRC

SM2 (2.035"-40)
Extra-Thick Retaining Ring

POLARIS-SM1RR

SM1 (1.035"-40)
Stainless Steel Retaining Ring

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Retaining Rings Selection Guidea

Standard Retaining Rings: Ø5 mm to Ø1/2"
Standard Retaining Rings: Ø13 mm to Ø1"
Standard Retaining Rings: Ø30 mm to Ø1.5"
Standard Retaining Rings: Ø39 mm to Ø2"
Standard Retaining Rings: Ø75 mm to Ø4"
Extra-Thick Retaining Rings
Stress-Free Retaining Rings
Plastic Retaining Rings
Stainless Steel Retaining Rings
  • Click "More" in each section of the table to view available retaining rings. Use the links in the table header to jump to a detailed web presentation with complete information for each retaining ring.

Features

  • Standard (Aluminum) Retaining Rings Available for Optics Ranging from Ø5 mm to Ø4"
  • Extra-Thick SM05-, SM1-, and SM2-Threaded Retaining Rings for High-Curvature Lenses
  • Stress-Free Retaining Rings are Compatible with the SM05, SM1, and SM2 Thread Standards
  • Delrin (Plastic) SM05- and SM1-Threaded Retaining Rings Provide Gentler Contact with Optic Surface
  • Stainless Steel SM05-, SM1-, and SM2-Threaded Retaining Rings for Our SM-Threaded Polaris Mounts
  • Standard Ø1/2", Ø1", and Ø2" Retaining Rings Available in Packs of 5 or 10

Thorlabs offers a wide selection of Retaining Rings for securing optical components into our threaded mounts, lens tubes, and unmounted optic adapters. Two retaining rings can be used to secure the optical component inside the center of a lens tube: one as a stopper and the other to lock in the component.

Depending on the size needed, these retaining rings are available in one or more of the following types: standard (aluminum), extra-thick, stress-free, plastic, or stainless steel. For a table of available options, please see the Retaining Rings Selection Guide to the right.

We offer extra-thick (5 mm) retaining rings which provide easier mounting for high-curvature lenses, such as aspheric lenses and condenser lenses (see the Lens Mounting Guide tab for more information). Our Stress-Free Retaining Rings (Item #'s SM05LTRR, SM1LTRR, and SM2LTRR) have a rubber O-ring that provides a light-tight seal around the optical components. The SM05PRR and SM1PRR Plastic Retaining Rings are produced from Delrin to provide gentler contact with an optic's surfaces than our standard retaining rings. Please keep in mind that due to the increased thickness of the stress-free and plastic retaining rings, the thickness of the optic that can be accommodated in the mount may be reduced. Finally, stainless steel retaining rings are ideal for use with our SM-threaded Polaris mirror mounts.

Thorlabs also offers a line of fixed-diameter and adjustable spanner wrenches for rings for optic diameters from 5 mm to 3" and spanner bits for SM05, SM1, SM2, and SM3 retaining rings. For using multiple thread types in the same setup, please see our extensive line of thread adapters.

For ordering convenience, the SM05RR and SM1RR Standard Retaining Rings are available in packs of 10, and the SM2RR Standard Retaining Ring is available in packs of 5.

Also available are spanner wrenches compatible with a number of our standard retaining rings. Scroll to the bottom of the page for more information.

Thorlabs' retaining rings are used to secure unmounted optics within lens tubes or optic mounts. These rings are secured in position using a compatible spanner wrench. For flat or low-curvature optics, standard retaining rings manufactured from anodized aluminum are available from Ø5 mm to Ø4". For high-curvature optics, extra-thick retaining rings are available in Ø1/2", Ø1", and Ø2" sizes.

Extra-thick retaining rings offer several features that aid in mounting high-curvature optics such as aspheric lenses, short-focal-length plano-convex lenses, and condenser lenses. As seen in the animation to the right, the guide flange of the spanner wrench will collide with the surface of high-curvature lenses when using a standard retaining ring, potentially scratching the optic. This contact also creates a gap between the spanner wrench and retaining ring, preventing the ring from tightening correctly. Extra-thick retaining rings provide the necessary clearance for the spanner wrench to secure the lens without coming into contact with the optic surface.

Thorlabs' Threading Specifications

Thorlabs' lens tubes utilize a series of non-standard threadings. Threading specifications are given below for our SM threadings utilized in our lens tube and cage system components so that you can machine mating components to suit your application. We also offer products with C-Mount and RMS threadings, and the specifications for these threadings are also given below. Please note that other manufacturers may have different tolerances for these threads. For other thread specifications that are not listed here, please contact Tech Support.


Click to Enlarge
SM05 Threading: Ø1/2" Lens Tubes, 16 mm Cage Systems
External Thread, 0.535"-40.0, UNS-2A Internal Thread, 0.535"-40.0, UNS-2B
Max Major Diameter 0.5340" Min Major Diameter 0.5350"
Min Major Diameter 0.5289" Min Pitch Diameter 0.5188"
Max Pitch Diameter 0.5178" Max Pitch Diameter 0.5230"
Min Pitch Diameter 0.5146" Min Minor Diameter (and 83.3% of thread) 0.508"
Max Minor Diameter 0.5069" Max Minor Diameter (and 64.9% of thread) 0.514"
RMS Threading: Objective, Scan, and Tube Lenses
External Thread, 0.800"-36.0, UNS-2A Internal Thread, 0.800"-36.0, UNS-2B
Max Major Diameter 0.7989" Min Major Diameter 0.8000"
Min Major Diameter 0.7934" Min Pitch Diameter 0.7820"
Max Pitch Diameter 0.7809" Max Pitch Diameter 0.7866"
Min Pitch Diameter 0.7774" Min Minor Diameter (and 83.3% of thread) 0.770"
Max Minor Diameter 0.7688" Max Minor Diameter (and 64.9% of thread) 0.777"
C-Mount Threading: Machine Vision Lenses, CCD/CMOS Cameras
External Thread, 1.000"-32.0, UN-2A Internal Thread, 1.000"-32.0, UN-2B
Max Major Diameter 0.9989" Min Major Diameter 1.0000"
Min Major Diameter 0.9929" Min Pitch Diameter 0.9797"
Max Pitch Diameter 0.9786" Max Pitch Diameter 0.9846"
Min Pitch Diameter 0.9748" Min Minor Diameter (and 83.3% of thread) 0.966"
Max Minor Diameter 0.9651" Max Minor Diameter (and 64.9% of thread) 0.974"
SM1 Threading: Ø1" Lens Tubes, 30 mm Cage Systems
External Thread, 1.035"-40.0, UNS-2A Internal Thread, 1.035"-40.0, UNS-2B
Max Major Diameter 1.0339" Min Major Diameter 1.0350"
Min Major Diameter 1.0288" Min Pitch Diameter 1.0188"
Max Pitch Diameter 1.0177" Max Pitch Diameter 1.0234"
Min Pitch Diameter 1.0142" Min Minor Diameter (and 83.3% of thread) 1.008"
Max Minor Diameter 1.0068" Max Minor Diameter (and 64.9% of thread) 1.014"
SM30 Threading: Ø30 mm Lens Tubes
External Thread, M30.5x0.5 Internal Thread, M30.5x0.5
Max Major Diameter 30.480 mm Min Major Diameter 30.500 mm
Min Major Diameter 30.371 mm Min Pitch Diameter 30.175 mm
Max Pitch Diameter 30.155 mm Max Pitch Diameter 30.302 mm
Min Pitch Diameter 30.059 mm Min Minor Diameter (and 83.3% of thread) 29.959 mm
Max Minor Diameter 29.938 mm Max Minor Diameter (and 64.9% of thread) 30.094 mm
SM1.5 Threading: Ø1.5" Lens Tubes
External Thread, 1.535"-40, UNS-2A Internal Thread, 1.535"-40, UNS-2B
Max Major Diameter 1.5339" Min Major Diameter 1.535"
Min Major Diameter 1.5288" Min Pitch Diameter 1.5188"
Max Pitch Diameter 1.5177" Max Pitch Diameter 1.5236"
Min Pitch Diameter 1.5140" Min Minor Diameter (and 83.3% of thread) 1.508"
Max Minor Diameter 1.5068" Max Minor Diameter (and 64.9% of thread) 1.514"
SM2 Threading: Ø2" Lens Tubes, 60 mm Cage Systems
External Thread, 2.035"-40.0, UNS-2A Internal Thread, 2.035"-40.0, UNS-2B
Max Major Diameter 2.0338" Min Major Diameter 2.0350"
Min Major Diameter 2.0287" Min Pitch Diameter 2.0188"
Max Pitch Diameter 2.0176" Max Pitch Diameter 2.0239"
Min Pitch Diameter 2.0137" Min Minor Diameter (and 83.3% of thread) 2.008"
Max Minor Diameter 2.0067" Max Minor Diameter (and 64.9% of thread) 2.014"
SM3 Threading: Ø3" Lens Tubes
External Thread, 3.035"-40.0, UNS-2A Internal Thread, 3.035"-40.0, UNS-2B
Max Major Diameter 3.0337" Min Major Diameter 3.0350"
Min Major Diameter 3.0286" Min Pitch Diameter 3.0188"
Max Pitch Diameter 3.0175" Max Pitch Diameter 3.0242"
Min Pitch Diameter 3.0133" Min Minor Diameter (and 83.3% of thread) 3.008"
Max Minor Diameter 3.0066" Max Minor Diameter (and 64.9% of thread) 3.014"

Posted Comments:
Xiaoyu Jiang  (posted 2019-07-24 19:18:39.24)
Our lab is trying to build a system in UHV and we are using some SM05RR rings. We are worried about the compatibility for the black anodized rings with UHV. Can you give some technical suggestions on this issue or provide quotes for UHV compatible retaining rings? Thanks.
YLohia  (posted 2019-07-25 10:03:18.0)
Hello, we do not recommend using SM05RR retaining rings in UHV applications due to outgassing of the anodization. Our stainless steel POLARIS-SM05RR retaining rings designed for our POLARIS mounts would be a more suitable choice.
chris  (posted 2017-06-12 08:51:23.777)
Unclear what I need. Have 30mm unmounted optics and want to install in SM2 tube. What item do I need? Thanks. CHris
tfrisch  (posted 2017-06-26 10:34:41.0)
Hello, thank you for contacting Thorlabs. You may want to look at AD2-30 or SM2AD30 on our 2" adapters page: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5324
rachid  (posted 2017-05-03 22:29:46.17)
I am planing to buy polarizer "LPVISE200-A" with a rotating mount "RSP2". what kind of ring is suitable for me so I can hold the polarizer ? Regards, Rachid
tcampbell  (posted 2017-05-03 11:53:06.0)
Response from Tim at Thorlabs: The RSP2 rotation mount has an SM2-threaded bore, which accepts SM2RR retaining rings. However, one SM2RR retaining ring is already included with the RSP2 mount to hold the optic against the mount's fixed retention lip.
christoph.bohr  (posted 2016-11-03 10:35:46.07)
Given the small torque used in tightening down the retaining rings I wonder if there is a recommended method for securing the retaining rings to keep them from working loose in a high vibration environment. Something like a thread locker but ideally something that still allows disassembly for service and does not interfere with the lens and coating material. regards C. Bohr
tfrisch  (posted 2016-11-04 09:26:04.0)
Hello, thank you for contacting Thorlabs. I will reach out to you directly to discuss your high vibration application.
tmorgus  (posted 2016-06-10 16:34:03.81)
Hello Cbrideau, Dito. This was a project that kept slipping to the back burner since there are alternative solutions. But it is nice to finally have the right solution available for highly curved optics. Sincerely, Tyler Mechanics Business Unit Leader
cbrideau  (posted 2016-06-10 15:32:13.92)
Glad to see these thick rings finally available! I'll be talking to my local distributor about getting some for holding large condenser lenses.
cbrideau  (posted 2016-02-22 11:54:32.26)
Would love to be able to get the extra-thick version of these for mounting Condenser lenses. These rings are used in your pre-built collimation mounts but thus far you don't sell them individually.
schach  (posted 2014-08-13 14:01:20.563)
Guten Tag, welches Gewinde besitzt der Sicherungsring SM18RR? In der Liste finde ich die Angabe M18,5x0,5, die dazugehörige Angabe in der Zeichnung lautet 0,750-40! Vielen Dank im voraus. Mit freundlichen Grüßen C.Schach
jlow  (posted 2014-08-13 08:48:36.0)
Response from Jeremy at Thorlabs: Thank you for bringing this to our attention. The correct thread is 0.750"-40 for the SM18RR. We will correct the thread call out on the website.
nick  (posted 2013-02-01 12:08:06.75)
Can you please clarify what the o-ring material is (for product SM05LTRR), as well as its lifetime rating in an ambient environment?
tcohen  (posted 2013-02-06 15:26:00.0)
Response from Tim at Thorlabs: The O-Ring is Buna-N. We have updated our presentation to include this information.
tcohen  (posted 2012-09-18 15:10:00.0)
Response from Tim at Thorlabs to Luis: These have a black anodized finish which is typically not suitable for UHV. I will contact you directly to discuss your requirements and provide a quote for a vacuum compatible version.
lgml1  (posted 2012-09-17 16:22:31.0)
Hello, this is very useful. I just wish to ask whether any the SM17RR is suitable for being used in ultra high vacuum (I'm designing a customised tuve for holding the lens). Cheers, Luis
tcohen  (posted 2012-07-19 13:04:00.0)
Response from Tim at Thorlabs: Thank you for contacting us. This will depend on the lens dimensions and material. Qualitatively, you want to use the minimum amount of torque required to secure the optic as overtightening will induce stress birefringence. That being said, the retaining rings should hold the optic in a much less stressful way at the point of contact than a setscrew for example. Stress-free retaining rings were designed with this in mind. I will contact you directly to continue this conversation.
sebastien.avila  (posted 2012-07-17 10:38:21.0)
Hello, What is the tightening torque that should not be exeed while using an SM18RR on a 18mm diameter convex lens? We want to have a standar procedure to mounting these lenses and we need to stablish the maximum torque allowed. Thank you.
tcohen  (posted 2012-06-19 10:55:00.0)
Response from Tim at Thorlabs: The external thread specifications for the M15.5-0.5 thread used on our SM15RR are Major Max 15.479, Major Min 15.371, Minor Max 14.938, Minor Min 14.757, Pitch Max 15.155 and Pitch Min 15.065.
jbowen  (posted 2012-06-18 08:51:32.0)
I would like to know the thread specification for this part. Please provide the minor, major, and pitch diameters with the minimum and maximum tolerances for each dimension.

Standard Retaining Rings: Ø5 mm to Ø1/2"

  • Standard Retaining Rings for Optics Ranging
    from Ø5 mm to Ø1/2"
  • Compatible with our Optic Mounts and Lens Tubes
  • SM05RR Retaining Rings Available in 10 Packs

Our Standard Retaining Rings are manufactured from anodized aluminum and are offered in sizes to match our optic mounts and lens tubes. They maximize the clear aperture while providing sufficient holding force. Securing an optic using a retaining ring is a stable method for holding the optic since the optic is retained along its entire edge instead of just at a few points. Each retaining ring is machined with two slots for compatibility with our selection of spanner wrenches.

Item # Thread Thickness Thread Specs Compatible Spanner Wrench Compatible Optic Mounts Clear Aperture
SM5RR M5.5 x 0.5 0.07" (1.7 mm) info SPW205 or SPW801 LMR5(/M), AD5T,
CPM05, SP07, MLH5(/M),
or SM1AD5		 Ø0.15"
(Ø3.8 mm)
SM6RR M6.5 x 0.5 0.07" (1.7 mm) info SPW206 or SPW801 LMR6(/M), AD6T,
CPM06, SP08, MLH6(/M),
or SM1AD6		 Ø0.19"
(Ø4.8 mm)
SM7RR M7.5 x 0.5 0.07" (1.7 mm) info SPW207 or SPW801 LMR7(/M), AD7T, SP09, 
MLH7(/M), or SM1AD7		 Ø0.23"
(Ø5.8 mm)
SM8RR M8.5 x 0.5 0.07" (1.7 mm) info SPW208 or SPW801 LMR8(/M), AD8T,
CPM08, SP10, MLH8(/M),
or SM1AD8		 Ø0.27"
(Ø6.9 mm)
SM9RR M9.5 x 0.5 0.07" (1.7 mm) info SPW209 or SPW801 LMR9(/M), AD9T,
CPM09, SP11, MLH9(/M),
or SM1AD9		 Ø0.31"
(Ø7.9 mm)
SM10RR M10.5 x 0.5 0.07" (1.7 mm) info SPW210 or SPW801 LMR10(/M), AD10T, SP12,
MLH10(/M), or SM1AD10		 Ø0.35"
(Ø8.8 mm)
SM11RR M11.5 x 0.5 0.07" (1.7 mm) info SPW211 or SPW801 AD11T, SP13, or SM1AD11 Ø0.36"
(Ø9.1 mm)
SM12RR M12.5 x 0.5 0.07" (1.7 mm) info SPW801 SP14 Ø0.40"
(Ø10.2 mm)
SM05RR(-P10) SM05 (0.535"-40) 0.07" (1.7 mm) info SPW603 or SPW801 Any Internally SM05-Threaded Mount Ø0.44"
(Ø11.0 mm)
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM5RR Support Documentation
SM5RRM5.5 x 0.5 Retaining Ring for Ø5 mm Lens Mounts
$10.50
Today
SM6RR Support Documentation
SM6RRM6.5 x 0.5 Retaining Ring for Ø6 mm Lens Mounts
$10.50
Today
SM7RR Support Documentation
SM7RRM7.5 x 0.5 Retaining Ring for Ø7 mm Lens Mounts
$10.50
Today
SM8RR Support Documentation
SM8RRM8.5 x 0.5 Retaining Ring for Ø8 mm Lens Mounts
$10.50
Today
SM9RR Support Documentation
SM9RRM9.5 x 0.5 Retaining Ring for Ø9 mm Lens Mounts
$10.50
Today
SM10RR Support Documentation
SM10RRM10.5 x 0.5 Retaining Ring for Ø10 mm Lens Mounts
$10.50
Today
SM11RR Support Documentation
SM11RRM11.5 x 0.5 Retaining Ring for Ø11 mm Lens Mounts
$10.50
Today
SM12RR Support Documentation
SM12RRM12.5 x 0.5 Retaining Ring for Ø12 mm Lens Mounts
$10.50
Lead Time
SM05RR Support Documentation
SM05RRSM05 Retaining Ring for Ø1/2" Lens Tubes and Mounts
$4.12
Today
SM05RR-P10 Support Documentation
SM05RR-P10SM05 Retaining Ring for Ø1/2" Lens Tubes and Mounts, 10 Pack
$37.08
Today

Standard Retaining Rings: Ø13 mm to Ø1"

  • Standard Retaining Rings for Optics Ranging from Ø13 mm to Ø1"
  • SM-Threaded Retaining Rings are Compatible with our SM Optic Mounts and Lens Tubes
  • Retaining Rings with RMS (0.800"-36) and C-Mount (1.00"-32) Threads Available
  • SM1RR Retaining Rings Available in 10 Packs

Our Standard Retaining Rings are manufactured from anodized aluminum and are offered in sizes to match our optic mounts and lens tubes. They maximize the clear aperture while providing sufficient holding force. Securing an optic using a retaining ring is a stable method for holding the optic since the optic is retained along its entire edge instead of just at a few points. Each retaining ring is machined with two slots for compatibility with our selection of spanner wrenches.

Our C-Mount-threaded (1.00"-32) retaining ring is ideal for securing optical components into our CMR lens mount or CP13 30 mm cage plate and C- or CS-Mount compatible CCD and CMOS cameras. This retaining ring is engraved with both the part number and "C-Mount" to distinguish it from our SM-threaded retaining rings.

Item # Thread Thickness Thread Specs Compatible Spanner Wrench Compatible Optic Mounts Clear Aperture
SM13RR M13.5 x 0.5 0.07" (1.7 mm) info SPW801 AD13T or SM1AD13 Ø0.43"
(Ø10.9 mm)
SM14RR M14.5 x 0.5 0.07" (1.7 mm) info SPW801 AD14T or SM1AD14 Ø0.46"
(Ø11.7 mm)
SM15RR M15.5 x 0.5 0.07" (1.7 mm) info SPW801 LMR15 (LMR15/M), AD15T,
CPM15, or SM1AD15		 Ø0.50"
(Ø12.7 mm)
SM16RR M16.5 x 0.5 0.08" (2.0 mm) info SPW801 AD16T or SM1AD16 Ø0.54"
(Ø13.6 mm)
SM17RR M17.5 x 0.5 0.08" (2.0 mm) info SPW801 AD17T or SM1AD17 Ø0.57"
(Ø14.5 mm)
SM18RR 0.750"-40 0.08" (2.0 mm) info SPW801 LMR18 (LMR18/M), AD18T,
CPN18, or SM1AD18		 Ø0.62"
(Ø15.7 mm)
SM19RR M19.5 x 0.5 0.08" (2.0 mm) info SPW801 AD19T or SM1AD19 Ø0.64"
(Ø16.3 mm)
RMSRR 0.800"-36 0.07" (2.0 mm) info SPW801 OMR (OMR/M), CP16, or HCS013 Ø0.67"
(Ø17.0 mm)
SM20RR M20.5 x 0.5 0.08" (2.0 mm) info SPW801 LMR20 (LMR20/M), AD20T,
CPM20, or SM1AD20		 Ø0.68"
(Ø17.3 mm)
CMRR 1.00"-32 0.08" (2.0 mm) info SPW801 CMR (CMR/M) or
CP13 (CP13/M)		 Ø0.87"
(Ø22.0 mm)
SM1RR(-P10) SM1 (1.035"-40) 0.08" (2.0 mm) info SPW606, SPW602, or SPW801 Any Internally SM1-Threaded Mount Ø0.90"
(Ø22.9 mm)
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM13RR Support Documentation
SM13RRM13.5 x 0.5 Retaining Ring for Ø13 mm Lens Mounts
$10.50
Today
SM14RR Support Documentation
SM14RRM14.5 x 0.5 Retaining Ring for Ø14 mm Lens Mounts
$10.50
Today
SM15RR Support Documentation
SM15RRM15.5 x 0.5 Retaining Ring for Ø15 mm Lens Mounts
$10.50
Today
SM16RR Support Documentation
SM16RRM16.5 x 0.5 Retaining Ring for Ø16 mm Lens Mounts
$10.50
Today
SM17RR Support Documentation
SM17RRM17.5 x 0.5 Retaining Ring for Ø17 mm Lens Mounts
$10.50
Today
SM18RR Support Documentation
SM18RR0.750"-40 Retaining Ring for Ø18 mm Lens Mounts
$10.50
Today
SM19RR Support Documentation
SM19RRM19.5 x 0.5 Retaining Ring for Ø19 mm Lens Mounts
$10.50
Today
RMSRR Support Documentation
RMSRRRMS Retaining Ring for RMS Lens Mounts
$11.69
Today
SM20RR Support Documentation
SM20RRM20.5 x 0.5 Retaining Ring for Ø20 mm Lens Mounts
$10.50
Today
CMRR Support Documentation
CMRR 1.00"-32 Retaining Ring for C-Mount and CS-Mount Lens Mounts and Cameras
$12.67
Today
SM1RR Support Documentation
SM1RRSM1 Retaining Ring for Ø1" Lens Tubes and Mounts
$4.64
Today
SM1RR-P10 Support Documentation
SM1RR-P10SM1 Retaining Ring for Ø1" Lens Tubes and Mounts, 10 Pack
$41.72
Today

Standard Retaining Rings: Ø30 mm to Ø1.5"

  • Standard Retaining Rings for Optics Ranging
    from Ø30 mm to Ø1.5"
  • Compatible with our Optic Mounts and Lens Tubes

Our Standard Retaining Rings are manufactured from anodized aluminum and are offered in sizes to match our optic mounts and lens tubes. They maximize the clear aperture while providing sufficient holding force. Securing an optic using a retaining ring is a stable method for holding the optic since the optic is retained along its entire edge instead of just at a few points. Each retaining ring is machined with two slots for compatibility with our selection of spanner wrenches.

Item # Thread Thickness Thread Specs Compatible Spanner Wrench Compatible Optic Mounts Clear Aperture
SM30RR SM30 (M30.5 x 0.5) 0.08" (2.0 mm) info SPW607 or SPW801 Any Internally SM30-Threaded Mount Ø1.10"
(Ø27.9 mm)
SM31RR M31.5 x 0.5 0.08" (2.0 mm) info SPW801 SM2AD31 Ø1.14"
(Ø29.0 mm)
SM32RR M32.5 x 0.5 0.08" (2.0 mm) info SPW801 SM2AD32 or C32 Ø1.18"
(Ø30.0 mm)
SM33RR M33.5 x 0.5 0.08" (2.0 mm) info SPW801 SM2AD33 Ø1.22"
(Ø31.0 mm)
SM34RR M34.5 x 0.5 0.08" (2.0 mm) info SPW801 SM2AD34 Ø1.26"
(Ø32.0 mm)
SM35RR M35.5 x 0.5 0.08" (2.0 mm) info SPW801 SM2AD35 Ø1.30"
(Ø33.0 mm)
SM36RR M36.5 x 0.5 0.08" (2.0 mm) info SPW801 SM2AD36 Ø1.34"
(Ø34.0 mm)
SM37RR M37.5 x 0.5 0.08" (2.0 mm) info SPW801 SM2AD37 Ø1.38"
(Ø35.0 mm)
SM38RR M38 x 0.5 0.10" (2.5 mm) info SPW801 SM2A20
or WFA4111		 Ø1.38"
(Ø34.9 mm)
SM1.5RR SM1.5 (1.535"-40) 0.10" (2.5 mm) info SPW801 LMR1.5 (LMR1.5/M) or SM2AD1.5 Ø1.37"
(Ø34.8 mm)
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM30RR Support Documentation
SM30RRSM30 Retaining Ring for Ø30 mm Lens Mounts
$11.74
Today
SM31RR Support Documentation
SM31RRM31.5 x 0.5 Retaining Ring
$13.32
Today
SM32RR Support Documentation
SM32RRM32.5 x 0.5 Retaining Ring
$13.32
Today
SM33RR Support Documentation
SM33RRM33.5 x 0.5 Retaining Ring
$13.32
Today
SM34RR Support Documentation
SM34RRM34.5 x 0.5 Retaining Ring
$13.32
Today
SM35RR Support Documentation
SM35RRM35.5 x 0.5 Retaining Ring
$13.32
Lead Time
SM36RR Support Documentation
SM36RRM36.5 x 0.5 Retaining Ring
$13.32
Today
SM37RR Support Documentation
SM37RRM37.5 x 0.5 Retaining Ring
$13.32
Today
SM38RR Support Documentation
SM38RRCustomer Inspired! M38 x 0.5 Retaining Ring
$13.52
Today
SM1.5RR Support Documentation
SM1.5RRSM1.5 Retaining Ring for Ø1.5" Lens Mounts
$10.50
Today

Standard Retaining Rings: Ø39 mm to Ø2"

  • Standard Retaining Rings for Optics Ranging
    from Ø39 mm to Ø2"
  • Compatible with our Optic Mounts and Lens Tubes
  • SM2RR Retaining Rings Available in 5 Packs

Our Standard Retaining Rings are manufactured from anodized aluminum and are offered in sizes to match our optic mounts and lens tubes. They maximize the clear aperture while providing sufficient holding force. Securing an optic using a retaining ring is a stable method for holding the optic since the optic is retained along its entire edge instead of just at a few points. Each retaining ring is machined with two slots for compatibility with our selection of spanner wrenches.

Item # Thread Thickness Thread Specs Compatible Spanner Wrench Compatible Optic Mounts Clear Aperture
SM39RR M39.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD39 Ø1.44"
(Ø36.5 mm)
SM40RR M40.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD40 Ø1.47"
(Ø37.5 mm)
SM41RR M41.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD41 Ø1.51"
(Ø38.5 mm)
SM42RR M42.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD42 Ø1.55"
(Ø39.5 mm)
SM43RR M43.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD43 Ø1.59"
(Ø40.5 mm)
SM44RR M44.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD44 Ø1.63"
(Ø41.5 mm)
SM45RR M45.5 x 0.5 0.10" (2.5 mm) info SPW801 LMR45 (LMR45/M) or SM2AD45 Ø1.67"
(Ø42.4 mm)
SM46RR M46.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD46 Ø1.71"
(Ø43.5 mm)
SM47RR M47.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD47 Ø1.75"
(Ø44.5 mm)
SM48RR M48.5 x 0.5 0.10" (2.5 mm) info SPW801 SM2AD48 Ø1.79"
(Ø45.5 mm)
SM2RR(-P5) SM2 (2.035"-40) 0.10" (2.5 mm) info SPW604 or SPW801 Any Internally SM2-Threaded Mount Ø1.90"
(Ø48.3 mm)
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM39RR Support Documentation
SM39RRM39.5 x 0.5 Retaining Ring
$13.32
Today
SM40RR Support Documentation
SM40RRM40.5 x 0.5 Retaining Ring
$13.32
Today
SM41RR Support Documentation
SM41RRM41.5 x 0.5 Retaining Ring
$13.32
Today
SM42RR Support Documentation
SM42RRM42.5 x 0.5 Retaining Ring
$13.32
Today
SM43RR Support Documentation
SM43RRM43.5 x 0.5 Retaining Ring
$13.32
Today
SM44RR Support Documentation
SM44RRM44.5 x 0.5 Retaining Ring
$13.32
Today
SM45RR Support Documentation
SM45RRM45.5 x 0.5 Retaining Ring for Ø45 mm Lens Mounts
$13.52
Today
SM46RR Support Documentation
SM46RRM46.5 x 0.5 Retaining Ring
$13.32
Today
SM47RR Support Documentation
SM47RRM47.5 x 0.5 Retaining Ring
$13.32
Today
SM48RR Support Documentation
SM48RRM48.5 x 0.5 Retaining Ring
$13.32
Today
SM2RR Support Documentation
SM2RRSM2 Retaining Ring for Ø2" Lens Tubes and Mounts
$7.11
Today
SM2RR-P5 Support Documentation
SM2RR-P5SM2 Retaining Ring for Ø2" Lens Tubes and Mounts, 5 Pack
$31.98
Today

Standard Retaining Rings: Ø75 mm to Ø4"

  • Standard Retaining Rings for Optics Ranging
    from Ø75 mm to Ø4"
  • Compatible with our Optic Mounts and Lens Tubes

Our Standard Retaining Rings are manufactured from anodized aluminum and are offered in sizes to match our optic mounts and lens tubes, are designed to maximize the clear aperture while providing sufficient holding force. Securing an optic using a retaining ring is a stable method for holding the optic since the optic is retained along its entire edge instead of just at a few points. Each retaining ring is machined with two slots for compatibility with our selection of spanner wrenches.

Item # Thread Thickness Thread Specs Compatible Spanner Wrench Compatible Optic Mounts Clear Aperture
SM75RR M75.5 x 0.5 0.16" (4.1 mm) info SPW801a LMR75 (LMR75/M) Ø2.81"
(Ø71.4 mm)
SM3RR SM3 (3.035"-40) 0.10" (2.5 mm) info SPW605 or SPW801a Any Internally SM3-Threaded Mount Ø2.81"
(Ø71.4 mm)
SM100RR M100.75 x 0.5 0.16" (4.1 mm) info N/A LMR100 (LMR100/M) Ø3.80"
(Ø96.4 mm)
SM4RR SM4 (4.035"-40) 0.13" (3.3 mm) info N/A LMR4 (LMR4/M) Ø3.81"
(Ø96.8 mm)
  • The blades of the SPW801 will overhang the inner edge of the SM75RR and SM3RR retaining rings. If you wish to mount a lens with a short focal length using one of these retaining rings with the SPW801, please contact Technical Support for additional information.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM75RR Support Documentation
SM75RRM75.5 x 0.5 Retaining Ring for Ø75 mm Mounts
$15.80
Today
SM3RR Support Documentation
SM3RRSM3 Retaining Ring for Ø3" Lens Tubes and Mounts
$15.80
Today
SM100RR Support Documentation
SM100RRM100.75 x 0.5 Retaining Ring for Ø100 mm Mounts
$18.40
Today
SM4RR Support Documentation
SM4RRCustomer Inspired! SM4 Retaining Ring for Ø4" Mounts
$18.40
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Extra-Thick Retaining Rings

  • Extra-Thick (5 mm) SM05-, SM1-, and SM2-Threaded Retaining Rings
  • Ideal for Use With High-Curvature Lenses Such as Aspheric Lenses and Condenser Lenses (See the Lens Mounting Guide Tab Above for More Information)

These extra-thick SM05, SM1, and SM2 retaining rings are manufactured from anodized aluminum and are designed with a 5 mm thickness for easier mounting of high-curvature lenses, such as aspheric lenses and condenser lenses. The SM threading on the outside of the ring does not extend down the entire thickness of the ring. For best performance, the retaining ring should be used with the non-threaded side contacting the lens. Please see the table below for a list of compatible spanner wrenches.

Item # Thread Thicknessa Thread Specs Compatible
Spanner Wrench		 Compatible
Optic Mounts		 Clear Aperture
SM05RRC SM05 (0.535"-40) 0.20" (5.0 mm) info SPW603 or SPW801 Any Internally SM05-Threaded Mount Ø0.44"
(Ø11.0 mm)
SM1RRC SM1 (1.035"-40) 0.20" (5.0 mm) info SPW606, SPW602, or SPW801 Any Internally SM1-Threaded Mount Ø0.90"
(Ø22.9 mm)
SM2RRC SM2 (2.035"-40) 0.20" (5.0 mm) info SPW604 or SPW801 Any Internally SM2-Threaded Mount Ø1.90"
(Ø48.3 mm)
  • The depth of the threading does not extend down the entire thickness of the ring.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM05RRC Support Documentation
SM05RRCExtra-Thick SM05 (0.535"-40) Threaded Retaining Ring
$9.95
Today
SM1RRC Support Documentation
SM1RRCExtra-Thick SM1 (1.035"-40) Threaded Retaining Ring
$11.15
Today
SM2RRC Support Documentation
SM2RRCExtra-Thick SM2 (2.035"-40) Threaded Retaining Ring
$13.32
Today

Stress-Free Retaining Rings

Stress-Free
Retaining Ring		 Clear Aperture Standard
Retaining Ring		 Clear Aperture
SM05LTRR Ø0.32" (Ø8.1 mm) SM05RR Ø0.44" (Ø11.0 mm)
SM1LTRR Ø0.82" (Ø20.8 mm) SM1RR Ø0.90" (Ø22.9 mm)
SM2LTRR Ø1.68" (Ø42.7 mm) SM2RR Ø1.90" (Ø48.3 mm)
  • Design Provides Reduced Stress Clamping Action
  • Provides Light-Tight Seal Around an Optic
  • Compatible with our Optic Mounts and Lens Tubes

Our Stress-Free Retaining Rings are available with our standard SM05, SM1, or SM2 threadings. This design uses an O-ring made of Buna-N nitrile rubber to reduce the stress on the optic surface and completely seal out sources of stray light. Like our standard retaining rings, our stress-free retaining rings contain two slots for compatibility with our selection of spanner wrenches.

Due to the rubber O-ring, the clear aperture is slightly reduced relative to our standard retaining rings. Please see the table to the upper right for details.

Item # Thread Thickness Thread Specs Compatible
Spanner Wrench		 Compatible
Optic Mounts
SM05LTRR SM05 (0.535"-40) 0.15" (3.8 mm) info SPW603 or SPW801 Any Internally SM05-Threaded Mount
SM1LTRR SM1 (1.035"-40) 0.16" (4.1 mm) info SPW602, SPW606, or SPW801 Any Internally SM1-Threaded Mount
SM2LTRR SM2 (2.035"-40) 0.18" (4.6 mm) info SPW604 or SPW801 Any Internally SM2-Threaded Mount
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM05LTRR Support Documentation
SM05LTRRSM05 (0.535"-40) Stress-Free Retaining Ring
$19.94
Today
SM1LTRR Support Documentation
SM1LTRRSM1 (1.035"-40) Stress-Free Retaining Ring
$23.70
Today
SM2LTRR Support Documentation
SM2LTRRSM2 (2.035"-40) Stress-Free Retaining Ring
$25.43
Today

Plastic Retaining Rings

Plastic
Retaining Ring		 Clear Aperture Standard
Retaining Ring		 Clear Aperture
SM05PRR Ø0.44" (Ø11.0 mm) SM05RR Ø0.44" (Ø11.0 mm)
SM1PRR Ø0.80" (Ø20.3 mm) SM1RR Ø0.90" (Ø22.9 mm)
  • Provide Gentler Contact with an Optic's Surfaces than Standard Retaining Rings
  • Compatible with our Optic Mounts and Lens Tubes

The SM05PRR and SM1PRR Delrin (Plastic) Retaining Rings provide gentler contact with the surface of optics than our standard retaining rings. They are compatible with any internally SM05- or SM1-threaded optic mount, respectively.

Each of these plastic retaining rings is thicker than the standard retaining ring of the same diameter featured above. Please note that due to the increased thickness, the maximum optic thickness that can be accommodated inside our standard SM05- and SM1-compatible mounts will be slightly diminished. In addition, the clear aperture of SM1PRR plastic retaining ring is slightly reduced compared to its standard counterpart.

Refer to the table below for compatible spanner wrench options, and see the table to the upper right for the diameter of each plastic retaining ring relative to our standard retaining rings.

Item # Thread Thickness Thread Specs Compatible
Spanner Wrench		 Compatible
Optic Mounts
SM05PRR SM05 (0.535"-40) 0.08" (2.0 mm)a info SPW603 or SPW801 Any Internally SM05-Threaded Mount
SM1PRR SM1 (1.035"-40) 0.11" (2.8 mm)a info SPW801 Any Internally SM1-Threaded Mount
  • Due to the increased thickness of the plastic retaining ring compared to its standard counterpart, the thickness of the optic that can be held in our various SM05- and SM1-compatible mounts may be decreased.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM05PRR Support Documentation
SM05PRRCustomer Inspired! SM05 (0.535"-40) Plastic Retaining Ring for Ø1/2" Lens Tubes and Mounts
$5.52
Today
SM1PRR Support Documentation
SM1PRRCustomer Inspired! SM1 (1.035"-40) Plastic Retaining Ring for Ø1" Lens Tubes and Mounts
$5.90
Today

Stainless Steel Retaining Rings

Stainless Steel
Retaining Ring		 Clear Aperture Standard
Retaining Ring		 Clear Aperture
POLARIS-SM05RR Ø0.43" (Ø10.9 mm) SM05RR Ø0.44" (Ø11.0 mm)
POLARIS-SM1RR Ø0.90" (Ø22.9 mm) SM1RR Ø0.90" (Ø22.9 mm)
POLARIS-SM2RR Ø1.90" (Ø48.3 mm) SM2RR Ø1.90" (Ø48.3 mm)

These stainless steel SM05, SM1, and SM2 retaining rings have identical thread specifications when compared to our standard SM05 (item # SM05RR), SM1 (item # SM1RR), and SM2 (item # SM2RR) retaining rings. They are designed for use with our SM-threaded Polaris mirror mounts. The matched material (stainless steel) helps reduce thermal hysteresis by having a matched coefficient of thermal expansion (CTE) to the Polaris mount. Please refer to the table below for compatible spanner wrench options, and see the table to the upper right for the diameter of each stainless steel retaining ring relative to our standard retaining rings.

Item # Thread Thickness Thread Specs Compatible
Spanner Wrench		 Compatible
Optic Mounts
POLARIS-SM05RR SM05 (0.535"-40) 0.07" (1.7 mm) info SPW603 or SPW801 Any Internally SM05-Threaded Mount
POLARIS-SM1RR SM1 (1.035"-40) 0.08" (2.0 mm) info SPW606, SPW602, or SPW801 Any Internally SM1-Threaded Mount
POLARIS-SM2RR SM2 (2.035"-40) 0.10" (2.5 mm) info SPW604 or SPW801 Any Internally SM2-Threaded Mount
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
POLARIS-SM05RR Support Documentation
POLARIS-SM05RRStainless Steel SM05 (0.535"-40) Threaded Retaining Ring
$7.58
Today
POLARIS-SM1RR Support Documentation
POLARIS-SM1RRCustomer Inspired! Stainless Steel SM1 (1.035"-40) Threaded Retaining Ring
$11.99
Today
POLARIS-SM2RR Support Documentation
POLARIS-SM2RRStainless Steel SM2 (2.035"-40) Threaded Retaining Ring
$10.83
Today

Spanner Wrenches for Retaining Rings

CT101 Application
Click to Enlarge
Stackable spanner wrenches, like the SPW603, can be fitted together to reach retaining rings in long lens tubes.
Spanner Wrench Application
Click to Enlarge
An SPW602 spanner wrench is used to place an optic in a lens tube via a retaining ring. This spanner wrench features an engraved scale to indicate spanner wrench depth.
  • Individual Sizes for Standard Retaining Rings
  • Knurled Handle for Improved Grip
  • Stackable Spanner Wrenches for Reaching Retaining Rings in Longer Lens Tubes

These spanner wrenches enable adjustment or installation of many of our standard retaining rings. The hollow construction of each spanner wrench allows the retaining ring to be adjusted without obscuring the beam path. They feature knurled handles for improved grip as well as flanges to keep the retaining ring on the end of the spanner wrench while inserting or removing the ring.

As shown to the right, the SPW602 features an engraved scale to indicate spanner wrench depth in both imperial and metric increments (0.1" and 0.5 mm, respectively), thereby enabling precise positioning of optics.

For retaining rings not covered by these cylindrical spanner wrenches, please see the SPW801 Adjustable Spanner Wrench sold at the bottom of the page. The SPW801 features an adjustable spanning range as well as long blades that extend 1.6" (40.7 mm) from the body of the wrench. Hence, for lenses with a high radius of curvature, we recommend using the SPW801 over the cylindrical spanner wrenches, whose guide flanges may come into contact with the lens.

 Item # SPW205 SPW206 SPW207 SPW208 SPW209 SPW210 SPW211 SPW603 SPW606 SPW602 SPW607 SPW604 SPW605
Compatible
Retaining Rings		 SM5RR SM6RR SM7RR SM8RR SM9RR SM10RR SM11RR SM05RR,
SM05RRC,
SM05LTRR,
SM05PRR,
POLARIS-SM05RR		 SM1RR,
SM1RRC,
SM1LTRR,
POLARIS-SM1RR		 SM1RR,
SM1RRC,
SM1LTRR,
POLARIS-SM1RR		 SM30RR SM2RR,
SM2RRC,
SM2LTRR,
POLARIS-SM2RR		 SM3RR
Feature Stackable: One End of Spanner Wrench Fits to End of Other Spanner
Wrench to Reach Retaining Rings in Longer Lens Tubes		 - Engraved Scale - - -
Length 1.00" 1.00" 1.00" 1.00" 1.00" 1.00" 1.00" 1.00" 1.00" 3.88" 4.35" 4.35" 4.35"
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SPW205 Support Documentation
SPW205Spanner Wrench for SM5RR Retaining Rings, Length = 1.00"
$19.10
Today
SPW206 Support Documentation
SPW206Spanner Wrench for SM6RR Retaining Rings, Length = 1.00"
$19.10
Today
SPW207 Support Documentation
SPW207Spanner Wrench for SM7RR Retaining Rings, Length = 1.00"
$19.10
Today
SPW208 Support Documentation
SPW208Spanner Wrench for SM8RR Retaining Rings, Length = 1.00"
$19.10
Today
SPW209 Support Documentation
SPW209Spanner Wrench for SM9RR Retaining Rings, Length = 1.00"
$19.10
Today
SPW210 Support Documentation
SPW210Spanner Wrench for SM10RR Retaining Rings, Length = 1.00"
$19.10
Today
SPW211 Support Documentation
SPW211Spanner Wrench for SM11RR Retaining Rings, Length = 1.00"
$19.10
Today
SPW603 Support Documentation
SPW603Spanner Wrench for SM05-Threaded Retaining Rings, Length = 1.00"
$26.00
Today
SPW606 Support Documentation
SPW606Customer Inspired! Spanner Wrench for SM1-Threaded Retaining Rings, Length = 1.00"
$28.38
Today
SPW602 Support Documentation
SPW602Spanner Wrench for SM1-Threaded Retaining Rings, Graduated Scale with 0.1"
(2.5 mm) Increments, Length = 3.88"
$28.38
Today
SPW607 Support Documentation
SPW607Customer Inspired! Spanner Wrench for SM30-Threaded Retaining Rings, Length = 4.35"
$43.50
Today
SPW604 Support Documentation
SPW604Customer Inspired! Spanner Wrench for SM2-Threaded Retaining Rings, Length = 4.35"
$47.22
Today
SPW605 Support Documentation
SPW605Spanner Wrench for SM3-Threaded Retaining Rings, Length = 4.35"
$83.02
Today
Additional Lens Tube Systems
  • Ø1/2" Lens Tubes

  • Ø1" Lens Tubes

  • Ø30 mm Lens Tubes

  • Ø1.5" Lens Tubes

  • Ø2" Lens Tubes

  • Ø3" Lens Tubes

  • C-Mount Extension Tubes

  • Lens Tube Mounts

  • Adapters and Accessories

  • Retaining Rings

  • Spanner Wrenches

  • Cage / Lens Tube Mounted Optics

  • Alignment Tools

  • SM1 Lens Tube Kit

  • SM2 Lens Tube Kit

  • SM1 Lens Tube & 30 mm Cage Kit

  • Lens Tube & Cage Extension Kit

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