Features 1、Improve Lubrication: Bearing adopts ceramic pelleting process, which greatly reduces the friction strength and improves the lubrication performance of the self lubricating system, improving the riding experience. 2、Effort Saving: Ceramic ball has self lubricating and maintenance free characteristics, provides silky smoothing rotation and higher transmission efficiency, effective save effort when riding. 3、High Compatibility: Reducer sleeve has good compatibility, riding without clamping chain, which is suitable for 8, 9, 10, 11 speed rear derailleur, installation shaft diameter compatible with 4mm, 5mm, 6mm. 4、Deep Tooth Design: Bicycle rear derailleur with deep tooth to reduce the chain off, provide stable chain to easily change speed, give you a satisfying using experience. 5、Metal Ceramic: Bike rear derailleur roller made of high quality metal ceramic material, with high strength and wear resistance, which has good performance for long service life. Item Type: Bicycle Rear Derailleur Pulley Material: Metal Ceramic Diameter: Approx. 5cm / 1.97in Package List 1 x Guide Wheel 2 x Reduction Sleeve