Description: *Brand new and high quality *Made of high-quality materials, ， *stainless steel ball inlaid in the retainer design. *replacement for the bicycle or racing bicycle or mountain bike. *21/20mm, outer diameter 21mm, steel ball diameter 4.763mm, often used in front hub *25mm, outer diameter 25mm, steel ball diameter 6.35mm, often used in rear hub *29-22mm, inner diameter 22mm, outer diameter 29mm, steel ball diameter 6.35mm, common bottom bracket on the market *31-22mm, inner diameter 22mm, outer diameter 31mm, steel ball 4.763mm, used for Bottom Bracket *37-29mm, inner diameter 29mm, outer diameter 37mm, steel ball diameter 4mm, commonly used in ordinary bicycle front fork headset Specification: Material: steel Color: silver quality: 10PCS size: 20mm， 25mm, 29mm, 31mm，37mm(options) Package Includes: 10PCS bearing Note: 1. The real color of the item may be slightly different from the pictures shown on website caused by many factors such as brightness of your monitor and light brightness. 2. Please allow slight manual measurement deviation for the data. Made from high-quality materials, our outdoor sports products are durable and affordable to meet your daily needs. Please check the product size and model before placing an order to ensure it is the product you need. When you encounter a problem, please contact us and we will help until the problem is perfectly solved. When you receive your product, whether you are satisfied or not, we want to hear your opinion. Every customer can enjoy free refund or exchange service for damaged/quality problem products.