Features1Multi Layer Plating and Anti Rust Treatment: High tension steel plate nickel chromium plating, multi layer plating and anti rust treatment, high accuracy tooth ratio. 2Concave and Convex Tooth Design: Concave and convex tooth design, make the speed change more gliding, weight reduction, and strong compatibility. Suitable for road bikes. 3Hollow Technology: Adopts hollow technology, can effectively and easily reduce the weight, so that riding easier, and more gliding. 4Runs Smoothly: The flywheel rotates smoothly and has no noise, and can well ensure that it is closely connected with the wheel hub of the bicycle and runs smoothly. 5Simple Operation: Simple to operate, easy to use, easy to install and disassemble. Without any difficult requirements even though you use it for the first time.SpecificationItem Type: 9 Speed 30T Cassette FreewheelWeight: Approx.369g / 13.0ozSpeed Ratio:11-13-15-17-19-21-23-25-30TMaterial: Nickel Chrome SteelApplicability: Suitable For Road Bikes and Folding BicyclesPackage List1 x Flywheel2 xSprockets1 x Flywheel Cover