Features: brand new and high quality 1# 40-32mmm, inner diameter 32mm, outer diameter 40mm, steel ball diameter 4mm, commonly used in MTB and Road bike front fork headset 2# 37-29mm, inner diameter 29mm, outer diameter 37mm, steel ball diameter 4mm, commonly used in ordinary bicycle front fork headset 3# 38-24mm, inner diameter 24mm, outer diameter 38mm, steel ball diameter 8mm, commonly used in children's bicycles 4# 31-22mm, inner diameter 22mm, outer diameter 31mm, steel ball 4.763mm, used for Bottom Bracket 5# 29-22mm, inner diameter 22mm, outer diameter 29mm, steel ball diameter 6.35mm, common bottom bracket on the market 6# 25mm, outer diameter 25mm, steel ball diameter 6.35mm, often used in rear hub 7# 21mm, outer diameter 21mm, steel ball diameter 4.763mm, often used in front hub Specification: Material: Steel Quantity: 2PCS The package includes: 2x bearing 【Utility and value】If a product is useful to you, it has value when we sell it. 【 Shopping cart 】 Buy multiple pieces at a time, the more affordable the price. 【 Good quality】Made of high-quality material, ensuring durability and practicality in usage. 【 After-sales service 】 Provide 48-hour after-sales service to quickly answer your questions.