This is a C-Mount for telescope cameras with a M28.5 mount that you want to adapt to a M48 scope mounting. This is effectively a 1.25-inch mount (M28.5) that adapts directly to a 2-inch mounting thread (M48). I use it for a SVBony SV305 camera and mount it directly to my SV550 but should work with any camera that uses the C-Mount going to a M48 male thread on the scope.
This adapter uses 20mm backfocus. If there are requests for other backfocus versions, I can upload additional profiles for 25, 30, 40, and 50.
Is it necessary… nah, but that shouldn't stop you from printing one :)