This sale is for a converter ring to allow fitting of Mamiya RB67 Pro/ProS lenses to the later ProSD (or RZ67) cameras. It is in near mint condition with just very minor paint loss around the edge.
This ring fits onto the back of your RB67 or RB67 C lens to make the correct fit with the later RB67 Pro SD or even RZ67 camera bodies. These have a larger lens throat and this adapter ring brings your lens up to the correct size. Dead easy to fit – you just push it on with the thicker end to the outside (easier to get off again if you need to!).