Features1The AL7075 aluminum alloy bottom bracket shell is made of aluminum alloy, which is sturdy and durable and has a long service life. 2Bearings provide better weight distribution and higher stability, thereby providing more efficient power transmission. 3Compared with the traditional bottom bracket, it has higher compatibility with the chain rings, better waterproof performance and quietness. 4Lightweight and easy to install. No need for professionals, you can also operate and install by yourself. 5Connect your crank arm and protect the stable and long lasting power applied to your transmission system.SpecificationItem Type: External Bearing Bottom ShaftMaterial: Aluminum AlloyOuter Diameter: Approx.47mm/1.9inInner Diameter: Approx.29mm/1.1inFive Links: 68/73Package List1 x Bicycle Bottom Axle2 x Washer