Sram X4 Derailleur bearing upgrade caps

thingiverse

The original Sram X4 derailleur gear doesn't have any bearing. The two caps of the gear are actually used as bearing Since the contact is between two plastic parts there's a lot of friction and at some point it becomes noisy. This parts (you need 2 of them) are just replacement caps which allow you to fit a 606 type bearing between the cap and the gear. I would recommend using double-sealed bearing (606ZZ is the exact part model in the catalogs) That way you are using a ball bearing and it's much smoother.