Designed to attach on this Canon EF/EF-S Adapter With Screw Holes. The Canon EF/EF-S adapter extends the mechanical tube length (MTL) slightly, and makes the spacing between the Canon sensor and the flange of the microscope objective 160mm. 

To use with other cameras, make sure you design the mounting mechanism to be exactly the correct height for achieving a MTL of 160mm. Canon EF and EF-S both have a flange focal distance of 44mm, which is the reason for the flange-to-flange distance of this design (including the Canon EF/EF-S mount) being 116mm. The RMS adapter itself (the design you are currently reading about) is 104.5 mm tall.

The design should be printed in black plastic with thick walls to avoid light bleeding through the print. Light-bleed will cause terrible images. To reduce internal reflections, the inner walls can be painted with a matte paint, but I have not found this necessary for my purposes.

The design uses 4mm tall M2.5 threaded inserts, and is designed for 16mm M2.5 screws.