BBB Pulleys Aluboys Ceramic is high quality aluminum derailleur pulleys with ceramic bearings. It has extra stiffness for fast shifting. High-quality sealed ceramic bearing. Super smooth and durable. Bearing type: Ceramic Compatible with Shimano 9, 10 and 11-speed (except RD-7900 and 7970) / Mega Range, SRAM X0/X9/X7, Apex, Rival, Force and Red (> 2011) and Campagnolo 11-speed. Made of Aluminum.