Description: All the results of the simulations and the experimentations indicated that the ceramic ball bearings' performances are very good, especially in the low load and high-speed environment. Specifications: specification Size:11T Structure: Ceramic bearing Material: aluminum alloy 7075 Color: Black Red Blue Silver Gold Weight: about 7.8g Fit for 4/5/6 MM roller screw axis Apply for most of rear derailleur on the market Package Included: Jockey Wheel*1 Notes: Please check the detail size/model information before purchasing. Due to the different monitor and light effect , the actual color of the item might be slightly different from the color showed on the pictures . Thanks for your understanding. Please allow 1-2 cmmeasuring deviation due to manual measurement. Chat with us should you need any assistance.