Strong stability - The design of ceramic bearings is self-lubricating and maintenance-free. It can effectively reduce the friction while increasing the riding speed and has strong stability. Deeper tooth marks - The design with deep tooth marks can effectively reduce the possibility of the bike falling off the chain. The speed is smoother and the chain is more stable. Note - Before buying, please check whether the diameter of the range where your guide wheel is installed is suitable for the maximum outer diameter of the 12T guide wheel. It must be able to accommodate a diameter of 50mm before installation. Multiple choices - The main body of the bearing is hollowed out, which is more portable and easier to use. There are black, blue, gold, red, four colors can be selected, you can choose your favorite color. High-quality materials - Made of high-quality aluminum alloy materials, with abrasion resistance and durability. The material is not easily deformed and has a long service life. Specficications: Material: 7075 Aluminum Alloy Weight: 11.6g Color: Black/ Gold/ Blue/ Red Specifications: 12T Size: 50 * 8.5mm Package Includes1 * Bicycle Tooth Wheel