1Aluminum Material: Made of high quality aluminum alloy with high strength, rust resistance and durability, no easy to deform. 2CNC Machining: CNC machining treatment can make the surface smooth, and can also prevent wear and tear. 3Size Situation: The inner diameter of locking cap is about 26mm/0in, outer diameter is about 44mm/7in. 4Universal Type: Can be used for barrel shaft, compatible with mountain bike, very easy to install and remove with the quick release whelset type. 5Using Method: Using with centerlock adapter, mount on the middle lock hub, 9/12/15/20mm axis are all available, so that it can install 6 bolt disc.