BBB gear accessories jockey wheels RollerBoys BDP-12 ceramic-black BDP-12 RollerBoys Ceramic Bearing Derailleur Pulleys  10T. Compatible with Shimano 9 and 10, Mega Range.  Composite material provided by EMS Swiss, with 40% glass-fiber mixture giving unmatched stiffness and precise shifting. Extremely high wear resistance.  All bushings for different shifting systems are included. *Equiped with ceramic bearings for ultra smooth gliding and almost no resistance. *Maintenace-free Set includes upper and lower pulleys with bushings.