I have been thinking about getting a RB67 for a while but don't know that much about them. I am currently using a Bronica ETRSi so I am familiar with medium format but think the bigger 6x7 negative would be nice. I know that there are 3 models Pro, ProS and ProSD and wonder what backs and lenses will work with which models. I have noticed backs that are 120, 220 and some that does both. Also are RB and RZ backs and lenses compatible. It seems that RBs are reasonably priced and I guess this is because studios have gone digital. Just wonder where others find a good source for used RBs and if it is better to try to get the complete camera or just find all the pieces and put one together.