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 BICYCLE BIKE HEADSET Bottom Bracket FORK BEARINGS All series 2Pcs. High-quality product,each process is strictly implemented in accordance with process standards. Perfect price-performance ratio, save you more money. We will ship it ASAP,when you place the order. If you have any questions,please feel free to contact us,we will solve it for you.