Features1[Durable]Al7075 aluminum alloy axle housing is made of aluminum alloy, which is durable and long service life 2[Long Life]A double silicone sealing rings is installed at the port at the bottom of the bracket. Prevent pollution, prolong service life and easy to install 3[Protective Effect]The screw system can protect the bike frame and output more power, which is better than the central shaft of ordinary structure 4[Important Accessories]An important accessory of bicycle, which supports the steady operation of bicycle 5[Steady Rotation]Easy to install, stable rotation, convenient installation and operation, and better quietnessSpecificationItem Type:Bottom BracketMaterial: Aluminum AlloyOuter Diameter: Approx. 47mm / 1.9inInner Diameter: Approx. 29mm / 1.1inBottom Bracket Shell: Built In Approx. 86mm / 3.4in,Approx.92mm / 3.6mmPackage List1 x BottomBracket2 xWasher