1、PRECISE CRAFTSMANSHIP: Crafted from 6061 aluminum alloy through a series of CNC milling, polishing, and anodizing processes, the ceramic rear derailleur pulley showcases a refined metal texture, with a lightweight hollow design for enhanced performance. 2、ENHANCED COMPATIBILITY: Featuring a new spring structure that prevents chain jamming, the 11 tooth design is suitable for 8, 9, 10, and 11 speed rear derailleurs, with an outer diameter compatible with 4, 5, and 6mm installation axles, ensuring smooth and silent rotation. 3、VERSATILE USE: Designed for both guide and tension pulleys, this pulley's spring fixed structure allows compatibility with both guide and tension pulleys, providing flexibility and convenience for a variety of setups. 4、SMOOTHLY ROTATION: Utilizing an oxidized zirconia ceramic ball, known as white ceramic, the ceramic rear derailleur pulley offers self lubricating easy maintenance, ensuring a smooth and seamless rotation experience. 5、IMPROVED TRANSMISSION EFFICIENCY: With a new spring fixed structure to prevent chain jamming, the ceramic rear derailleur pulley not only enhances pedaling efficiency but also guarantees smooth shifting and stable performance during rides. Item Type: Bike Ceramic Bearing Pulley Wheel Material: Ceramic, aluminum alloy 1 x Derailleur Pulley 2 x Reducing Sleeves