T2 Lens - Olympus OM 

Mount SLR Film Camera Lens Adapter

 OM10,0M1,0M2,0M4 ETC

used mounts in good condition, may differ from stock picture due to different makes,

 these fit the screw on T2 thread found on preset lenses and lens mounted adapters

 and telescope / microscope adapters

 - these will not fit M42 pentax screw fit lenses (the thread pitch is different)