These collimation caps are a simple, portable tool for quickly checking and adjusting the alignment of your reflector telescope's optics.
 
Each cap is 3D printed from durable, environmentally friendly PLA polymer and has a highly reflective disc on the inside that makes it easy to use.
Unlike other collimation caps, it has an ergonomic rim for easy removal.
 
The size is 1.25" and it is a universal snug fit.