Originally Posted by
TimmyT
I just sold a 13-16-20-26-31 Regina, so at least a 31, probably larger. Don't ask me how they chose 31. I haven't a clue, and I counted the teeth 3 times because I was completely befuddled.
The 60's Campy Record RDs are marked 13-31 on the back - maybe mates up with those.