Ø2" Lens Tubes

Directly Accepts Ø2" (50.8 mm) Optics
Compatible with SM2-Threaded Components
Designed for use with Our 60 mm Cage Systems

SM2L30C

SM2L30

SM2M10

SPW604

Spanner Wrench

SM05L10

SM1L10

SM2L10

SM3L10

SM1A1

SM1A2

SM3A2

Easily Interface with Other Lens Tube Sizes

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Overview
Application
Threading Specs
Feedback

Ø2" Shortcuts
Lens Tube Couplers SM Thread Adapters Lens Tube Mounts End Caps Kinematic Mounts Fixed Lens Mounts Rotational Mounts Translation Mounts

Additional Lens Tube Sizes
Ø1/2" Ø1" Ø30 mm Ø1.5" Ø3"

Features

Variety of Lens Tubes in Lengths from 0.33" (8.4 mm) to 3.96" (100.6 mm)
- Standard Lens Tubes
- Lens Tubes without External Threading
- Slotted Lens Tubes for Access to Optics without Disassembly
Extension Tube for Optics with Long Focal Lengths
Wide Range of SM2 (2.035"-40) Compatible Optomechanical Components
Compatible with Our 60 mm Cage Systems
Lens Tubes Directly Accept Ø2" (50.8 mm) Optics

Lens tubes are ideal for creating compact optical subassemblies with light-tight beam paths. The Ø2" lens tubes sold here can be used to house one or several optical elements, as shown in the diagram of a beam expander below. In addition to the Ø2" lens tubes featured on this page, Thorlabs also offers Ø1/2", Ø1", Ø30 mm, Ø1.5", and Ø3" versions, each of which is equipped with an SM series thread standard that depends on the tube diameter. Vacuum-compatible versions of our Ø1/2" and Ø1" stackable lens tubes are available from stock; customers can request vacuum-compatible lens tubes at other lengths and diameters by contacting Tech Sales.

Optics are separated and secured by retaining rings that are positioned at the desired depth within the lens tube using our SPW604 spanner wrench. Depending on the item purchased, one or two retaining rings will be included (see below for details). Additional retaining rings can be purchased separately.

Click to Enlarge
When an engraved lens tube is attached to another lens tube, the engraving of the connected end is no longer visible.

Lens Tube Compatible Products
Thread Adapters	Terminated Fiber Adapters	Fixed Fiber Collimator Adapters	Kinematic Fiber Collimator Adapters	LED Mounts	LD Mounts	Aspheric Lens Mounts	Irises, Apertures, and Shutters	Alignment Tools

Parts List^a
#	Product Description	Qty.	Photo (Click to Enlarge)
1	Microscopy Camera	1
2	SM1A9 - Adapter with External C-Mount Threads and Internal SM1 Threads	1
3	SM1ZM - Non-Rotating SM1 Zoom Housing for Ø1" Optics	1
4	SM1L03 - SM1 Lens Tube	1
5	SM1A2 - Adapter with External SM1 Threads and Internal SM2 Threads	1
6	SM2L39 - Lens Tube Spacer for Tube Lenses	1
7	TTL200-A - Widefield Imaging Tube Lens^b	1
8	SM2A59 - Adapter with Male D1N Dovetail and Internal SM2 Threads	1

This assembly is optimized for tube lenses with a working distance of 151.88 ± 1.75 mm; an alternate lens tube spacer should be used for tube lenses with a different working distance. Use the following link to add all of the items needed to make this adjustable C-mount to SM2 camera tube to your cart: View Product List

Item #	Qty	Description
SM1A9	1	Adapter with External C-Mount Threads and Internal SM1 Threads, 4.4 mm Spacer
SM1ZM	1	SM1 Zoom Housing for Ø1" Optics, Non-Rotating, 3.5 mm Travel
SM1L03	1	SM1 Lens Tube, 0.30" Thread Depth, One Retaining Ring Included
SM1A2	1	Adapter with External SM1 Threads and Internal SM2 Threads
SM2L39	1	SM2 Lens Tube, 3.9" Thread Depth, One Retaining Ring Included
TTL200-A	1	Tube Lens, f = 200 mm, ARC: 350 - 700 nm, External SM2 Threads
SM2A59	1	Adapter with Male D1N Dovetail and Internal SM2 Threads

This adjustable C-mount to SM2 camera tube can also be constructed using the TTL200-S8, TTL200-B, TTL200MP, and TTL200MP2 tube lenses.

Adjustable C-Mount to SM2 Camera Tube for Widefield and Telecentric Tube Lenses

In the following example, an adjustable C-mount to SM2 camera tube is created to attach a custom widefield imaging assembly to a DIY Cerna microscope. An SM1A9 Adapter (2) is used to connect a C-mount Microscopy Camera (1) to the SM1ZM Zoom Housing (3). An SM1L03 Lens Tube (4) provides extra thread depth to allow full travel of the zoom housing, and an SM1A2 Adapter (5) converts the SM1 threads to SM2 threads. An SM2L39 Lens Tube Spacer* (6) positions the camera at the appropriate working distance from an attached infinity-corrected Tube Lens or Telecentric Tube Lens (7). The SM2A59 Adapter (8) enables the optical assembly to be connected to a DIY Cerna Microscope via a D1N dovetail.

Components used in the configuration pictured below are listed in the table to the right. These parts, along with optomechanical components used to construct a DIY Cerna microscope, are sold separately.

*The lens tube is designed to position the camera at the image plane of the tube lens when the SM1ZM Zoom Housing is at the center of its adjustment range, allowing for ±1.75 mm travel.

Click to Enlarge
An adjustable C-mount to SM2 adapter can be constructed to attach custom widefield imaging assemblies to DIY Cerna microscopes.

Click to Enlarge

Threading Specifications

The following is a general overview of screw threading. For more details regarding specifications and dimensions, please consult the Machinery's Handbook, available for purchase at many bookstores.

Features of a Thread
A thread consists of three repeating features: a crest, flank, and root (see drawing to the right). Except in special cases, threads have symmetrical sides inclined at equal angles when a vertical line is drawn through the center of a crest or root. The distance between corresponding points on adjacent threads is known as the pitch of the thread. The flank angle is defined as the angle the flank makes with a perpendicular ray drawn from the screw axis. Unless otherwise stated, threads have a flank angle of 30°, resulting in a total angle between flanks of 60°. Each feature is shown in the diagram to the right.

The major diameter is taken from the crests of a thread while the minor diameter is taken from the roots. For most screws, crests and roots do not terminate at a sharp point, so crest and root truncation values are included in the definitions of major and minor diameter. The pitch diameter is approximately halfway between the major and minor diameters.

Thread Form
A thread form is a set of rules that define the features' scale relative to one another. Common thread forms include the Unified Screw Thread Form, used in the United States of America and measured in imperial units, and the ISO Metric Screw Thread Form, used in many parts of the world and measured with the International System of Units. There are many thread forms in the Unified screw thread standard designated by either UN, which defines a flat root contour, or UNR, which defines a round root contour. These can be further described by appending more letters. For example, an extremely fine thread with a flat root contour is designated UNEF. Those forms which are not standardized by the Unified screw thread system are designated UNS.

Thread Series
Most screws are identified by their thread series. Thread series are denoted by the major diameter and density of threads. Unified threads specify density in threads per inch, while Metric threads specify the thread pitch. For example, in the Unified nomenclature, a 1/4"-20 cap screw has a 1/4" diameter barrel and the pitch is 20 threads per inch (TPI). In metric nomenclature, an M4 x 0.7 cap screw has a 4 mm barrel and the pitch is 1 thread per 0.7 mm. The term M4 x 0.7 is often shortened to just M4.

Unified Thread Class Tolerancing
Location	Loose	Optimal	Strict
Internal	1B	2B	3B
External	1A	2A	3A

Metric Thread Tolerance Positions
Location	Loose	Optimal	Strict
Internal	-	G	H
External	e or f	g	h

Metric Thread Tolerance Grades
Dimension	Location	Tolerance Grades^a
Minor Diameter	Internal	4, 5, 6, 7, 8
Major Diameter	External	4, 6, 8
Pitch Diameter	Internal	4, 5, 6, 7, 8
Pitch Diameter	External	3, 4, 5, 6, 7, 8, 9

The tolerance becomes looser as the grade increases. The underlined grades are used with normal lengths of thread engagement.

Thread Class
The tolerances and allowances on a thread series are given by a thread class. Unified thread classes are alphanumeric identifiers starting with a number from 1 through 3, where 1 is the loosest tolerance and 3 is the tightest, and either A for external threading or B for internal threading.

Metric threads have a slightly more complex tolerancing method that uses tolerancing grades, designated by a number 3 through 9; and tolerancing positions, which use letters e through h. Grades provide a measure of the tolerance itself: the smaller the number, the tighter the tolerance. Positions denote the distance of the tolerance from the pitch diameter. Uppercase positioning letters indicate internal threads while lowercase positioning letters indicate external threads.

Quoting from the Machinery's Handbook, 29th Edition, p. 1885: "To designate the tolerance class, the grade and position of the pitch diameter is shown first followed by that for the major diameter in the case of the external thread or that for the minor diameter in the case of the internal thread, thus 4g6g for an external thread and 5H6H for an internal thread. If the two grades and positions are identical, it is not necessary to repeat the symbols, thus 4g, alone, stands for 4g4g and 5H, alone, stands for 5H5H."

Thorlabs' SM Series Threads
Threading specifications for our SM threads, utilized in our lens tube and cage system components, are given below so that you can machine mating components to suit your application. Most SM series threads utilize a non-standard Unified thread form, indicated by the letters UNS, with a 30° flank angle and a thread class of 2A and 2B. The exception is our SM30 series thread, which is a Metric thread form with a 30° flank angle and a tolerance of 6H/6g. We also offer products with C-Mount and RMS threads, and the specifications for these threads are given below for reference. Please note that other manufacturers may have different tolerances for C-Mount and RMS threads. For other thread specifications that are not listed here, please contact Tech Support.

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, M30.5 x 0.5 – 6H/6g		Internal Thread, M30.5 x 0.5 – 6H/6g
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"

SM4 Threading: Ø4" Lens Tubes
External Thread, 4.035"-40 UNS-2A		Internal Thread, 4.035"-40.0 UNS-2B
Max Major Diameter	4.0337"	Min Major Diameter	4.0350"
Min Major Diameter	4.0286"	Min Pitch Diameter	4.0188"
Max Pitch Diameter	4.0175"	Max Pitch Diameter	4.0245"
Min Pitch Diameter	4.0131"	Min Minor Diameter (and 83.3% of Thread)	4.008"
Max Minor Diameter	4.0066"	Max Minor Diameter (and 64.9% of Thread)	4.014"

Posted Comments:

Shan Xu (posted 2021-08-13 23:04:29.707)

Could you offer a 2 mm version of your 2.5mm SM2RR retaining rings?

cdolbashian (posted 2021-08-19 03:05:35.0)

Thank you for reaching out to us at Thorlabs with this request. I have contacted you directly regarding regarding the feasibility of this custom version of the SM2RR.

Ludovic A. (posted 2021-01-22 09:51:33.083)

Could you offer a 4" and/or 5" version of your 6" SM2 thick wall Extension tube? While it's acceptable to stack shorter tubes to reach the desired length, your current offering of SM2 tubes stops at 3.5" and jumps to 6". Intermediate versions of SM2 extension tubes would be much welcome (thick walled would be best, they could also be stackable (as your SM2Lxx) or without ext. thread (SM2Exx)). My current application makes use of a large format and heavy line scan lens with a long flange focal distance and I regularly use long lengths of SM2 tubes in other applications.

YLohia (posted 2021-01-22 01:56:03.0)

Thank you for your feedback. We will consider adding other lengths of these lens tubes to our catalog in the future. For immediate customizations, quotes can be requested by clicking the "Request Quote" button above. We will discuss this customization directly.

Van Van Rudd (posted 2020-08-03 11:55:09.33)

Are the lens tubes vacuum compatible? Could you make ones that are?

YLohia (posted 2020-08-03 02:04:10.0)

Thank you for contacting Thorlabs. These lens tubes are anodized and, thus, not vacuum-compatible. Custom unanodized versions can be requested by emailing techsupport@thorlabs.com.

Max D (posted 2019-06-04 05:17:05.527)

Hi Thorlabs team, I would like to know what is the tolerance on tilt of a flat surface within your SM2M10 tube by using SM2 retainer ring. Regards.

llamb (posted 2019-06-05 08:32:19.0)

Hello, thank you for contacting Thorlabs. The exact tip/tilt of an optic will greatly depend on the optic's flatness/parallelism as well as the lens tube. I have reached out to you directly to discuss this lens tube's tolerances and your application's needs further.

ger.folkersma (posted 2016-06-30 04:53:01.43)

Hi, the Solidowrks model of the SM2L15 seems to be corrupted. All other tube models work fine.

s.kovalev (posted 2015-10-13 20:29:52.873)

Hello. Do you have 2'' tubes with 6'' length or can you make it for us. Thanks Sergey.

besembeson (posted 2015-10-13 03:57:52.0)

Response from Bweh at Thorlabs USA: Yes we do. It seems the SM2E60 may be suitable for you - http://www.thorlabs.com/thorproduct.cfm?partnumber=SM2E60

cqtttv (posted 2013-07-22 17:48:37.463)

What is the tolerance on the diameter and sphericity?

jlow (posted 2013-07-22 15:58:00.0)

Response from Jeremy at Thorlabs: I will contact you directly to discuss about your application and provide this information.

Ø2" Stackable Lens Tubes

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SM2-Threaded (2.035"-40) Bore Accepts Ø2" (Ø50.8 mm) Optics
Stackable Design Enables Multi-Element Optical Systems
Compatible with Our 60 mm Cage Assembly Systems

These stackable Ø2" Lens Tubes provide a fast and easy means for building compact optical assemblies. Their stackable design and direct interfacing with all SM2-threaded (2.035"-40) components provide flexibility for complex optomechanical assemblies. One SM2RR Retaining Ring is included with each lens tube.

Click to Enlarge
An SM2L15 lens tube used to mount a SOLIS-1A high-powered LED.

Item #	L	Internal Thread Depth
SM2L03	0.33" (8.4 mm)	0.30" (7.6 mm)
SM2L04^a	0.47" (11.9 mm)	0.44" (11.0 mm)
SM2L05	0.53" (13.5 mm)	0.50" (12.7 mm)
SM2L10	1.03" (26.2 mm)	1.00" (25.4 mm)
SM2L15	1.53" (38.9 mm)	1.50" (38.1 mm)
SM2L20	2.03" (51.6 mm)	2.00" (50.8 mm)
SM2L27^a	2.73" (69.4 mm)	2.70" (68.6 mm)
SM2L30	3.03" (77.0 mm)	3.00" (76.2 mm)
SM2L32^a	3.24" (82.2 mm)	3.21" (81.4 mm)
SM2L39^a	3.96" (100.6 mm)	3.93" (99.8 mm)

This lens tube can be used as a spacer with our Infinity-Corrected Tube Lenses to create an adjustable C-mount to SM2 adapter that can be integrated into our Cerna^® DIY Microsocopy Systems. The following optomechanical components are needed: View Product List

Item #	Qty	Description
SM1A9	1	Adapter with External C-Mount Threads and Internal SM1 Threads, 4.4 mm Spacer
SM1ZM	1	SM1 Zoom Housing for Ø1" Optics, Non-Rotating, 3.5 mm Travel
SM1L03	1	SM1 Lens Tube, 0.30" Thread Depth, One Retaining Ring Included
SM1A2	1	Adapter with External SM1 Threads and Internal SM2 Threads
SM2A59	1	Adapter with Male D1N Dovetail and Internal SM2 Threads

. Please see the Application tab for details.

Alternatives	Ø1/2", Ø1", Ø30 mm, Ø1.5", and Ø3" Stackable Lens Tubes	Ø1" Lens Tube Extensions	Ø1" Lens Tubes with Side Access Ports

Based on your currency / country selection, your order will ship from Newton, New Jersey

+1 Qty Docs Part Number - Universal Price Available

SM2L03 SM2 Lens Tube, 0.3" Thread Depth, One Retaining Ring Included

$25.77

In Stock

SM2L04 NEW!SM2 Lens Tube, 0.4" Thread Depth, One Retaining Ring Included

$27.00

In Stock

SM2L05 SM2 Lens Tube, 0.5" Thread Depth, One Retaining Ring Included

$28.42

In Stock

SM2L10 SM2 Lens Tube, 1" Thread Depth, One Retaining Ring Included

$33.19

In Stock

SM2L15 SM2 Lens Tube, 1.5" Thread Depth, One Retaining Ring Included

$34.05

In Stock

SM2L20 SM2 Lens Tube, 2" Thread Depth, One Retaining Ring Included

$34.61

In Stock

SM2L27 NEW!SM2 Lens Tube, 2.7" Thread Depth, One Retaining Ring Included

$38.00

In Stock

SM2L30 SM2 Lens Tube, 3" Thread Depth, One Retaining Ring Included

$40.79

In Stock

SM2L32 NEW!SM2 Lens Tube, 3.2" Thread Depth, One Retaining Ring Included

$42.00

In Stock

SM2L39 SM2 Lens Tube, 3.9" Thread Depth, One Retaining Ring Included

$48.00

Lead Time

Ø2" Lens Tubes Without External Threads

Ø2in Lens Tubes Without External Threads

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SM2-Threaded (2.035"-40) Bore Accepts Ø2" (Ø50.8 mm) Optics
Unlike Stackable Lens Tubes, Optics can be Accessed from Both Ends
Use Lens Tube Couplers to Stack Multiple Lens Tubes
Allows Coupling of Two Components with External SM2 Threading
Directly Compatible with Our 60 mm Cage Assembly Systems

Unlike our Ø2" stackable lens tubes featured above, these Internally Threaded Lens Tubes do not feature a lip at one end nor do they have external SM2 threading. Therefore, optics housed inside can be accessed from both ends. To join these lens tubes end-to-end, use an SM2T2 Lens Tube Coupler. Two SM2RR Retaining Rings are included with each lens tube.

Alternatives	Ø1/2" and Ø1" Lens Tubes Without External Threads

Based on your currency / country selection, your order will ship from Newton, New Jersey

+1 Qty Docs Part Number - Universal Price Available

SM2M05 Customer Inspired! SM2 Lens Tube Without External Threads, 0.5" Thread Depth, Two Retaining Rings Included

$29.71

In Stock

SM2M10 Customer Inspired! SM2 Lens Tube Without External Threads, 1" Thread Depth, Two Retaining Rings Included

$32.97

In Stock

SM2M15 SM2 Lens Tube Without External Threads, 1.5" Thread Depth, Two Retaining Rings Included

$33.85

In Stock

SM2M20 Customer Inspired! SM2 Lens Tube Without External Threads, 2" Thread Depth, Two Retaining Rings Included

$35.94

In Stock

SM2M25 SM2 Lens Tube Without External Threads, 2.5" Thread Depth, Two Retaining Rings Included

$36.83

In Stock

SM2M30 Customer Inspired! SM2 Lens Tube Without External Threads, 3" Thread Depth, Two Retaining Rings Included

$38.91

In Stock

SM2M35 SM2 Lens Tube Without External Threads, 3.5" Thread Depth, Two Retaining Rings Included

$40.39

In Stock

Slotted Lens Tubes

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Easy Access to Optics
Rotatable Slip Shield Protects Optics
Compatible with SM2-Threaded Components

These stackable Ø2" Lens Tubes with side slots provide a fast and easy means for building complex optical assemblies and adjusting the optics without disassembling the setup. Several optics can be inserted into a single tube using multiple SM2RR Retaining Rings. Simply thread the first retaining ring to the desired depth, add the optic, and then use a second retaining ring to secure the optic. Optics can be manually adjusted via the side slots without the use of a spanner wrench. The rotatable slip shield included with the lens tube fits over the lens tube slots to prevent unwanted light from entering the system and to keep the optical setup free from debris. Two retaining rings and one black plastic dust cover are included with each lens tube.

Alternatives	Ø1/2" and Ø1" Slotted Lens Tubes

SM2 Extension Tubes

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The SM2E60 6" Long Extension Tube is designed to enable longer distances between optical components in lens tube systems that utilize lenses with large focal lengths. Although the ends of these extension tubes are threaded to accept our SM2 series stackable lens tubes, they feature thicker walls than our standard lens tubes, which leads to greater rigidity.

Alternatives	Ø1" Lens Tube Extensions

Ø2" Retaining Rings and Spanner Wrenches

Ø2in Retaining Rings and Spanner Wrenches

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Retaining Ring Specs
Item #	Material	Feature	Thickness	Inner Diameter
SM2RR	Black Anodized Aluminum	Standard	0.10" (2.5 mm)	1.90" (48.3 mm)
SM2RRV	Unanodized Aluminum	Vacuum Compatible^a	0.10" (2.5 mm)	1.90" (48.3 mm)
SM2LTRR	Black Anodized Aluminum	Rubber O-Ring for Stress-Free Mounting	0.18" (4.5 mm)	1.68" (42.7 mm)
SM2RRC	Black Anodized Aluminum	5 mm Thick for High-Curvature Lenses	0.20" (5.0 mm)	1.90" (48.3 mm)
POLARIS-SM2RR	Stainless Steel	Vacuum Compatible^b	0.10" (2.5 mm)	1.90" (48.3 mm)

>10^-6 Torr Vacuum Compatibility as Packaged; Lower Pressures with Additional Cleaning and Processing
>10^-5 Torr at 25 °C Vacuum Compatibility as Packaged without Bake Out; >10^-9 Torr at 25 °C with Proper Bake Out

Five Types of Retaining Rings for Securing Ø2" Optics
SPW604 Hollow Spanner Wrench Providing Unobstructed Beam Path During Adjustment
SPW801 Adjustable Spanner Wrench Accommodates Diameters from 0.12" (3.0 mm) to 2.89" (73.4 mm)

The SM2RR is our standard anodized aluminum retaining ring that ships with our Ø2" lens tubes as well as many other Thorlabs components and is available individually and in packs of 5. We offer five different SM2-threaded (2.035"-40) retaining rings, shown in the table to the right, which have unique features and can replace an SM2RR retaining ring. Please keep in mind that due to the increased thickness of some retaining rings, the maximum optic thickness that can be housed inside our standard SM2-compatible mounts will be diminished in some cases.

Spanner Wrenches
We offer two spanner wrench choices that can be used with these retaining rings. The SPW604 Spanner Wrench has a hollow design that enables retaining rings for our SM2 lens tubes to be adjusted and installed without obscuring the beam path. The handle is knurled for improved grip. Alternatively, the SPW801 Adjustable Spanner Wrench can also be used to position SM2-threaded retaining rings. Please note that the SPW801 wrench can withstand a maximum torque of 80 inch-pounds. We also offer the SPB2 Spanner Bit, which can be used with a standard 1/4" hex driver (sold separately). The SPB2 is included as part of the SPB600 Spanner Wrench Bit Kit.

Alternatives	Ø1/2", Ø1", and Ø3" Fixed Spanner Wrenches	Ø1/2", Ø1", Ø1.5", and Ø3" Retaining Rings