Cage System Overview
The Cage Assembly System provides a convenient way to construct large optomechanical systems with an established line of precision machined building blocks designed for high flexibility and accurate alignment. Among the most essential of these fundamental components are cage plates and cage assembly rods.

16mm, 30mm, and 60mm Cage System Standards
Thorlabs offers three standards defined by the center-to-center spacing of the cage assembly rods (see image to right). The 16mm SP series is designed for use with Ø1/4" and Ø1/2" optics. The 30mm cage standard, using CP series cage plates, is ideally suited for compact assemblies based around Ø1/2" and Ø1” optics. Lastly, the 60mm cage standard, using LCP series cage plates, is designed for Ø1” and Ø2” optics.

Standard Mating Parts
The flexibility inherent to the Cage Assembly System lies within its reliance on well-defined mounting and thread standards designed for direct interfacing with a wide range of specialized products.

The three most prevalent thread standards are our SM05 series (0.535”-40 thread), SM1 series (1.035”-40 thread), and SM2 series (2.035”-40 thread), all of which were defined to house the industries most common optic sizes. Essential building blocks, such as our popular lens tubes, directly interface to these standards.


A broad range of optomechanical positioning mounts and rigid construction components are designed for interfacing with the 16mm, 30mm, and 60mm cage assembly rod spacing. (See Visual Navigation Product Overview).

Dimensions of Standard Plates
16mm 30mm 60mm
Thread Series SM05 SM1 SM2
Hole to Hole Length 16mm, 0.63″ 30mm, 1.18″ 60mm, 2.36″
Total Length 25mm, 0.98″ 41mm, 1.60″ 71.1mm, 2.8″
Total Depth 6.35mm, 0.25″ 8.9mm, 0.35″ 12.7mm, 0.50″