My "23" Graphic pin roller w/ knob RH-8 does not fit in my RB67 Pro S. There is an extra rib on it. Just a note.
Of course if it did fit I'd be wasting film, but the RB 120 backs are going for a premium these days since there is so little 220 about.
Also, from my experience with several, the rb67 backs seem to be a weak point in system, both for light leaks and mechanical gremlins.