Video cameras, CCTV cameras and also some special astronomical cameras (e.g. Imaging Source) have the C-Mount or CS mount thread for adaptation. This adaptor serves as an adaptation to the standard T2 thread.
Standard adaptors are much longer in mechanical length. As a result they might cause focusing problems if additional parts are required in front of the camera. This special adaptor has an ultra low profile to afford sufficient space for additional adaptors. One particularly frequent adaptation is for off axis guiding and astro imaging with a filter wheel where a low profile T2 adaptation is often paramount and each millimetre might count!
