Long story short. KEH sent me the wrong part but instantly sent out the correct one (for the RB). They really stood up to the plate. So, in my first dealing with them ever (from a retail sales POV) they passed with flying colors.
They said 'Do NOT send it back'.
So, anyone want an extension ring for an RZ67 for, say, just s/h? PM me with zip code/location and I will let you know postage from 19963. I will send via USPS.
They said it worked. I have no RZ to test it with. So don't expect a guarentee but I don't see a problem here. Be advised.