1、This bike cassette is made of high strength steel nickel plated material, has greater wear resistance, durability, high temperature resistance, corrosion resistance, rust prevention, no deformation, good impact resistance due to the hardening technology. 2、The unique mountain bike chain design can well control the speed change function. Professional manufacturing, direct replacement of old or damaged flywheels, excellent accessories for mountain bikes and road bikes, easy to install, without any adjustments to the transmission system. 3、Easy to use, the hollow design can easily reduce weight, reduce the burden of riding, and achieve a good balance between strength and weight; reinforced aluminum frame, all over the mud hole, effective speed change; it is an ideal choice to reduce the weight of the bicycle. 4、Independent small tooth rings, the small teeth of the bicycle cassette flywheel are often used during use, and the independent small tooth design isconvenient for future replacement and maintenance. High accuracy toothprofiles, strong compatibility. 5、Provides fast and accurate indexing conversion function through special tooth profiles and slope. Lost tooth design, irregularly shaped and irregular cut angle tooth profiles, better compatible with various brands of gear shifting chains, and shifts and shifts flexibly and smoothly. Item Type: Bike Cassette Material: Steel Nickel Plated Product Size: Approx. 115mm/4.5in Diameter Speed: 9 Speed Number of Gear Teeth: 11-13-15-17-19-21-23-25-28T 1 x Bicycle Flywheel 2 x Sprocket 1 x Lock Loop