1、Ceramic Bearing: The rear derailleur wheel adopts ceramic bearing, which have good lubricity and flexible rotation, can make the speed change smoother. 2、Deep Tooth Design: The deep tooth guide wheel can effectively reduce the chain drop, the speed change is clearer, and the winding is more stable. 3、Fine Processing: Using 7075 high strength aluminum alloy CNC machining, anodizing treatment and hollow design, has good wear resistance and lightweight. 4、Circlip Design: The rear derailleur guide wheel is circlip design, which does not jam the chain when riding, and is suitable for chain guide wheels and tension wheels. 5、Strong Compatibility: The original aperture is 6mm, and it can be converted to 4mm or 5mm by installing the reducing tube, suitable for 8 9 10 11 speed transmission system. Item Type: Bike Rear Derailleur Wheel Material: Aluminum alloy + ceramic bearing Diameter: Approx. 50.5mm / 2in Applicable Transmission System: For 4mm 5mm 6mm screw aperture; for 8 9 10 11 speed system 1 x Rear Derailleur Wheel 2 x Reducing Sleeves