Nested Rotation Mounts


  • Optic Carriage Rotates Within Mounting Ring
  • Models Available for Ø1" and Ø2" Optics
  • 8-32 (M4) Tap for Post Mounting

LM1-B

Mounting Ring with Thumbscrew Retention

LM1-A

Optic Carriage

DLM1

Mounting Ring with
Magnetic Retention
(Includes Two DLM1-A
Carriages)

DLM1-A

Optic Carriage

DLM1-A

Optic Carriage

Related Items


Please Wait

Features

  • Optic Mounts with Interchangeable Rotating Optic Carriage
  • SM1- (1.035"-40) or SM2-Threaded (2.035"-40) Optic Carriage
  • Retaining Ring(s) Included for Secure Optic Mounting
  • Laser Engraved Scale with Graduations Every 2°, Labeled Every 20°
  • 8-32 (M4) Tap for Post Mounting

These nested lens mounts systems consist of an inner optic carriage that rotates within the outer mounting ring. Single (LM1-B and LM2-B) and dual (DLM1) rotational optic versions are available. The optic carriages are radially laser engraved to allow for precise rotational changes. The optic carriages are retained within the mounting ring by either a thumbscrew or magnetic attachment. Additional optic carriages can be purchased and used for easy exchange of optics. 

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 Gradesa
Minor Diameter Internal 4, 5, 6, 7, 8
Major Diameter External 4, 6, 8
Pitch Diameter Internal 4, 5, 6, 7, 8
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"

Rotation Mount and Stage Selection Guide

Thorlabs offers a wide variety of manual and motorized rotation mounts and stages. Rotation mounts are designed with an inner bore to mount a Ø1/2", Ø1", or Ø2" optic, while rotation stages are designed with mounting taps to attach a variety of components or systems. Motorized options are powered by a DC Servo motor, 2 phase stepper motor, piezo inertia motor, or an Elliptec™ resonant piezo motor. Each offers 360° of continuous rotation.

Manual Rotation Mounts

Rotation Mounts for Ø1/2" Optics
Item # MRM05(/M) RSP05(/M) CRM05 PRM05(/M)a SRM05 KS05RS CT104
Click Photo
to Enlarge
Features Mini Series Standard External SM1
(1.035"-40) Threads
Micrometer 16 mm Cage-Compatible ±4° Kinematic Tip/Tilt Adjustment Plus Rotation Compatible with 30 mm Cage Translation Stages and 1/4" Translation Stagesb
Additional Details
  • This mount is available in the PRM05GL5 bundle, which includes the PRM05 rotation mount with the SM05PM5 polarizing prism mount.
  • The CT104 is complatible with the 1/4" translation stages using our MS103(/M) adapter plate.
  • The CT104 is compatible with the CT1A(/M) cage translation stage, which is designed for use with 30 mm cage systems.

Rotation Mounts for Ø1" Optics
Item # RSP1(/M) LRM1 RSP1D(/M) DLM1(/M) CLR1(/M) RSP1X15(/M) RSP1X225(/M) PRM1(/M)a
Click Photo
to Enlarge
LRM1
Features Standard External SM1
(1.035"-40) Threads
Adjustable Zero Two Independently Rotating Carriages Rotates Optic Within
Fixed Lens Tube System
Continuous 360° Rotation
or 15° Increments
Continuous 360° Rotation
or 22.5° Increments
Micrometer
Additional Details
  • This mount is available in the PRM1GL10 bundle, which includes the PRM1 rotation mount with the SM1PM10 polarizing prism mount.

Rotation Mounts for Ø1" Optics
Item # LM1-A &
LM1-B(/M)
CRM1T(/M) CRM1LT(/M) CRM1PT(/M) KS1RS K6XS
Click Photo
to Enlarge
Features Optic Carriage Rotates Within Mounting Ring 30 mm Cage-Compatiblea 30 mm Cage-Compatible
for Thick Opticsa
30 mm Cage-Compatible
with Micrometera
±4° Kinematic Tip/Tilt Adjustment Plus Rotation Six-Axis
Kinematic Mounta
Additional Details
  • This mount also features four 4-40 (M3) holes on the rotation dial for use with the K6A1(/M) prism platform.

Rotation Mounts for Ø2" Optics
Item # RSP2(/M) RSP2D(/M) PRM2(/M) LM2-A &
LM2-B(/M)
LCRM2A(/M) KS2RS K6X2
Click Photo to Enlarge
Features Standard Adjustable
Zero
Micrometer Optic Carriage Rotates Within Mounting Ring 60 mm Cage-Compatible ±4° Kinematic Tip/Tilt Adjustment Plus Rotation Six-Axis Kinematic Mount
Additional Details
Rotation Drive Mechanism and Adjustment Range Manual, 360° Continuous Coarse: Manual, 360° Continuous;
Fine: ±7° Micrometer
Manual, 360° Continuous
Optic Mounting Internally SM2-Threaded Carriage Internal SM2 Threads
in LM2-A
Internally SM2-Threaded Carriage
Maximum Accepted Optic Thickness 0.51" (13 mm) 0.54" (13.7 mm) 0.48" (12.2 mm) 0.46" (11.7 mm) 0.52" (13.2 mm) 0.47" (12 mm) 0.53" (13.4 mm)
Post Mounting 8-32 (M4) Tap 8-32 (M4) Tap in LM2-B 8-32 (M4) Tap Four Counterbores for 8-32 (M4) Cap Screws Six Counterbores for 8-32 (M4) Cap Screws
Cage System Compatibility N/A Four 4-40 (M3) Taps on Rotation Dial
with 60 mm Spacing
N/A Four Bores for
Ø6 mm Cage Rods
with 60 mm Spacing
N/A N/A

Manual Rotation Stages

Manual Rotation Stages
Item # RP005(/M) PR005(/M) MSRP01(/M) RP01(/M) RP03(/M) QRP02(/M)
Click Photo
to Enlarge
Continuous Rotation Mount
Features Standard Two Hard Stops
Additional Details

Manual Rotation Stages
Item # XRNR1(/M) XRR1(/M) PR01(/M) CR1(/M) XYR1(/M) OCT-XYR1(/M)
Click Photo
to Enlarge
Features Fine Rotation Adjuster and
2" Wide Dovetail Quick Connect
Fine Rotation Adjuster and
3" Wide Dovetail Quick Connect
Fine Rotation Adjuster and
SM1-Threaded Central Aperture
Fine Pitch Worm Gear Rotation and 1/2" Linear XY Translation
Additional Details
  • The stage profile is higher when it is mounted using the screw slots rather than stacked on another stage or accessory with mating dovetails.
  • The OCT-XYR1(/M) stage includes the XYR1A solid sample plate. This plate can be detached from the stage to reveal the same mounting features present on the XYR1(/M) stage.

Motorized Rotation Mounts and Stages

Motorized Rotation Mounts and Stages with Central Clear Apertures
Item # DDR25(/M) PDR1C(/M) PDR1(/M) PDR1V(/M) PDXR1(/M)
Click Photo
to Enlarge
DDR25 PDR1C PDR1 PDR1V PDXR1
Features Compatible with
SM05 Lens Tubes,
16 mm Cage System, &
30 mm Cage System
Compatible with
16 mm Cage System
Compatible with
SM05 Lens Tubes &
30 mm Cage System
Vacuum-Compatible;
Also Compatible with
SM05 Lens Tubes &
30 mm Cage System
Compatible with
SM05 Lens Tubes &
30 mm Cage System
Additional Details

Motorized Rotation Mounts and Stages with Central Clear Apertures
Item # K10CR1(/M) PRM1Z8(/M)a DDR100(/M) ELL14 HDR50(/M)
Click Photo
to Enlarge
ELL14
Features Compatible with SM1 Lens Tubes & 30 mm Cage System Compatible with
SM1 Lens Tubes,
16 mm Cage System,
30 mm Cage System
Compatible with
SM1 Lens Tubes,
Open Frame Design for
OEM Applications
Compatible with
SM2 Lens Tubes
Additional Details
  • This stage is available in the KPRMTE(/M), which includes the PRMTZ8(/M) Motorized Rotation Stage with the KDC101 K-Cube DC Servo Motor Controller.
Motorized Rotation Mounts and Stages with Tapped Platforms
Item # PRMTZ8(/M)a ELL18(/M)b
Click Photo
to Enlarge
Features Tapped Mounting Platform for Mounting Prisms or Other Optics Tapped Mounting Platform, Open Frame Design for OEM Applications
Additional Details
  • This stage is available in the KPRM1E(/M), which includes the PRMT1Z8(/M) Motorized Rotation Stage with the KDC101 K-Cube DC Servo Motor Controller.
  • This stage is available in the ELL18K(/M), which includes an interface board, mounting brackets, and connectors for PC control.

Posted Comments:
jjurado  (posted 2011-09-02 14:06:00.0)
Response from Javier at Thorlabs to wjlentz: Thank you very much for your feedback. We will look into offering a version for 3" diameter optics of our LM1 and LM2 mounts. I will contact you directly for further discussion.
wjlentz  (posted 2011-09-01 14:38:13.0)
I need the 3" version of the rotating optical mount.
Back to Top

Nested Rotation Mount for Ø1" Optics


Click to Enlarge

The optic carriage is locked in place by a thumbscrew and can be easily removed from the main body of the mount.
  • Mount Ø1" Optics up to 0.37" (9.4 mm) Thick
  • Optic Carriage (LM1-A) and Mounting Ring (LM1-B or LM1-B/M) Sold Separately
  • Rotating Optic Carriage is Interchangeable for Quick Swapping
  • SM1-Threaded Optic Bore in Rotating Optic Carriage
  • Post Mountable via 8-32 (M4) Tap
  • Laser Engraved Graduation Marks Every 2°, Labeled Every 20°

The LM1-A optic carriage can be nested inside of the LM1-B (LM1-B/M) mounting ring and offers 360° of continuous rotation for Ø1" optics. The optic bore of the LM1-A carriage features internal SM1 (1.035"-40) threading and can hold an optic up to 0.37" (9.4 mm) thick with the included SM1RR retaining ring or an optic in an SM1-threaded housing. The carriage attaches to the main body of the mount using a thumbscrew. To remove the carriage from the mount, simply loosen the thumbscrew. Extra LM1-A interchangeable rotating carriages are available to allow optics to be swapped out quickly and easily.

Each carriage has a 360° laser-engraved scale marked at 2° increments for precise, repeatable positioning. The top-located thumbscrew can be tightened to lock the rotation of the optic carriage and, along with the double bore on the mount, maintains a stable, three-point contact to hold the optic carriage. When the LM1-A is properly fastened in the LM1-B by the thumbscrew, the optic axis is 1.04" (26.3 mm for the LM1/B) above the top of the post.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
LM1-B Support Documentation
LM1-BRotation Mounting Ring for LM1-A Ø1" Optic Carriage, 8-32 Tap
$28.15
3-5 Days
+1 Qty Docs Part Number - Universal Price Available
LM1-A Support Documentation
LM1-ARotating Inner Carriage for Ø1" Optics, One SM1RR Retaining Ring
$24.23
3-5 Days
+1 Qty Docs Part Number - Metric Price Available
LM1-B/M Support Documentation
LM1-B/MRotation Mounting Ring for LM1-A Ø1" Optic Carriage, M4 Tap
$28.15
3-5 Days
Back to Top

Dual Nested Rotation Mount for Ø1" Optics


Click to Enlarge

The rotating optic carriages can be easily removed from the main body of the mount.
  • Mount Two Ø1" Optics up to 0.25" (6.4 mm) Thick
  • Two Optic Carriages (DLM1-A) Included with DLM1
  • Each Optic Carriage Rotates Independently
  • Rotating Optic Carriages are Interchangeable for Quick Swapping
  • SM1-Threaded Optic Bore in Each Rotating Optic Carriage
  • Two SM1RR Retaining Rings Included
  • Post Mountable via 8-32 (M4) Tap

The DLM1(/M) Dual Rotation Mount includes two independently rotating carriages (item # DLM1-A) for Ø1" optics that offer 360° of continuous rotation. The optic bore of the DLM1-A carriage features internal SM1 (1.035"-40) threading and can hold an optic up to 0.25" (6.4 mm) thick with the included SM1RR retaining ring or an optic in an SM1-threaded housing. The carriages magnetically attach to the main body of the mount. To remove a carriage from the mount, simply pull the carriage off the main body. Another carriage can then be snapped on in its place. Extra DLM1-A interchangeable rotating carriages are available to allow optics to be swapped out quickly and easily.

Each carriage has a knurled edge for adjusting rotation and a 360° laser-engraved scale marked at 2° increments for precise, repeatable positioning. Two top-located setscrews can be tightened with a 5/64" (2.0 mm) hex key or balldriver to lock the rotation of the optic carriages independently. When the rotation is locked, the double bore on the mount maintains a stable, three-point contact to hold the optic carriage.

The DLM1 mount is designed to put the optic axis 1.00" (25.0 mm for the DLM1/M) above the top of the post When two optics are mounted, the separation between them is 0.30" (7.6 mm). The dual rotation mount is ideal for creating variable polarizers and attenuators by mounting linear polarizers and wave plates in close proximity without having to align the optic axes of two separate rotation mounts. We do not recommend using this mount with lens tubes, as the torque applied to the optic bore may overcome the magnetic attachment.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
DLM1 Support Documentation
DLM1Dual Rotation Mount for Ø1" Optics, Two Interchangeable Rotating Carriages, 8-32 Tap
$145.58
Lead Time
+1 Qty Docs Part Number - Universal Price Available
DLM1-A Support Documentation
DLM1-AInterchangeable Rotating Carriage for DLM1(/M), One SM1RR Retaining Ring
$34.95
3-5 Days
+1 Qty Docs Part Number - Metric Price Available
DLM1/M Support Documentation
DLM1/MDual Rotation Mount for Ø1" Optics, Two Interchangeable Rotating Carriages, M4 Tap
$145.58
3-5 Days
Back to Top

Nested Rotation Mount for Ø2" Optics

  • Mount Ø2" Optics Up to 0.46" (11.7 mm) Thick
  • Optic Carriage (LM2-A) and Mounting Ring (LM2-B or LM2-B/M) Sold Separately
  • Rotating Optic Carriage is Interchangeable for Quick Swapping
  • SM2-Threaded Optic Bore in Rotating Optic Carriage
  • Post Mountable via 8-32 (M4) Tap
  • Laser Engraved Scale with Graduations Every 2°, Labeled Every 20°

The LM2-A optic carriage can be nested inside of the LM2-B (LM2-B/M) mounting ring and offers 360° of continuous rotation for Ø2" optics. The optic bore of each carriage features internal SM2 (2.035"-40) threading and can hold an optic up to 0.46" (11.7 mm) thick with the included SM2RR retaining ring an optic in an SM2-threaded housing. The carriage attaches to the main body of the mount using a thumbscrew. To remove the carriage from the mount, simply loosen the thumbscrew. Extra LM2-A interchangeable rotating carriages are available to allow optics to be swapped out quickly at easily.

Each carriage has a 360° laser-engraved scale marked at 2° increments for precise, repeatable positioning. The top-located thumbscrew can be tightened to lock the rotation of the optic carriage and, along with the double bore on the mount, maintains a stable, three-point contact to hold the optic carriage. When the LM2-A is properly fastened in the LM2-B by the thumbscrew, the optic axis is 1.45" (36.8 mm for the LM2-B/M) above the top of the post.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
LM2-B Support Documentation
LM2-BRotation Mounting Ring for LM2-A Ø2" Optic Carriage, 8-32 Tap
$35.64
3-5 Days
+1 Qty Docs Part Number - Universal Price Available
LM2-A Support Documentation
LM2-ARotating Inner Carriage for Ø2" Optics, One SM2RR Retaining Ring
$32.08
3-5 Days
+1 Qty Docs Part Number - Metric Price Available
LM2-B/M Support Documentation
LM2-B/MRotation Mounting Ring for LM2-A Ø2" Optic Carriage, M4 Tap
$35.64
3-5 Days