The TS FA 240 fits into 2" focusers and has a male T-2 thread on the camera side. So you can adapt nearly any camera via the T-2 system. The T-2 thread (M-42x0,75 mm) is the connection to bajonet rings to all common SLR cameras.
40mm additional length can make sense: Many telecopes have their focal plane beyond the maximum focuser travel. They are intended for the use of 2" diagnoal and need an extension if a camera is used. The TS FA 240 contains a 40mm extension and so the focus problem can be solved without the need of an addtional adapter.
Safety groove The safety groove prevents the accessories from falling out if the locking screw is accidentally slightly loosened. This improves the safety of your equipment.
2" filter thread On its base, the adapter has a M48 thread for 2" filters. So you can use your filters also photographically.