Features： 1、Easy to install, no need to adjust the transmission system, the unique mountain bike chain design, can well control the transmission function. 2、Hollow design can easily reduce the weight, reduce the cycling burden, in the strength and weight of a good balance, easy to install and use. 3、Through the special tooth shape and incline to provide fast, accurate indexing conversion function, within the range of 9 speed to provide a stable gear, accurate positioning. 4、Bicycle flywheel is made of high strength steel, using hardening technology, with greater wear resistance, durability, high temperature resistance, corrosion resistance, rust resistance, no deformation. 5、Strong compatibility,fit for Sram 9 speed drive systems (except for SRAM XD). Specification： Item Type: Bicycle Freewheel Color: As Pictures Shown Material: High-strength Steel Speed: 9 Speed Weight: Approx. 300g/10.6oz Number of Gear Teeth: 11-12-13-15-17-19-21-24-28T Package List： 1 x Bicycle Freewheel 3 x Ring Gear 1 x Lock Ring