This adapter allows using most of microscope objectives (with RMS mount thread that is 0.8"-36tpi) on cameras with M42x1 lens mount thread (Zenit, Paktica etc).Also, if you have M42 to your camera adapter, you can use microscope objectives with movie cameras, camcorders, DSLRs etc.Made of light alloy (aluminium D16T), anodized and laser engraved.