Description:The pulley is made of aluminum alloy, so that it is very firm, lightweight and durable. Anti-rust and corrosion resistant. It run on smooth ball bearings, and it's a necessary accessory for your bicycle. There are four different colors for you to choose from, to meet different needs. Hope you will enjoy your cycling. Have a nice day.Features:1. Made of CNC aluminum alloy, lightweight and durable.2. Anti rust and corrosion resistant anodized.3. These pulleys run on smooth ball bearings.4. A necessary accessory for your bicycle.5. Fits for almost all mountain bike of 11T or 13T.Specifications:Material: Aluminum AlloyColor: Black, Red, Golden, SilverWeight: approx. 13g, 16gTeeth: 11T, 13T (optional)11T Diameter: approx. 40mm / 1.57"Hole Diameter: approx. 5mm / 0.19"13T Diameter: approx. 49mm / 1.92"Hole Diameter: approx. 5mm / 0.19"Compatible: Suitable for 4/5/6mm spindle shaft rollersPackage Included:1 x 11T/13T pulley wheel