I used this 2" visual back with my LOMO mak until I sold the mak. It threads onto the back of any SCT or mak and allows you to use a 2" refractor diagonal, so if you have both an SCT or mak and a refractor, you can use the same diagonal on both scopes. I found this to be very handy. It has two brass screws that compress the ring, so it doesn't leave set screw marks on your diagonal or two inch eyepieces. Doesn't have a brand name on it, but it is high quality aluminum and in mint condition. Someone told me it may by made by AP.
Cell number is 209-601-2636 if you wish to call.