Shimano shift wheels for Ultegra 11v (RD-6800/6870)

Shimano shift wheels for Ultegra 11v (RD-6800/6870) The sheaves or pulleys of the derailleur are responsible for transmitting the movement of the derailleur to the chain and regulating its tension, therefore, they are parts subject to wear and are responsible for the proper functioning and smoothness of the derailleur.