The first generation Biopace had a more pronounced shape which is described as an egg shaped curve and not an oval, the second generation Biopace is less egg shaped and less effective at what the system is designed to do.

Installed these yesterday... the 44 and 50 were new in the box while the 28 was a gently used spare.



Need a 46 to get a perfect half step gearing with the 6 speed block.