Hollow technology can easily reduce weight and make riding lighter, and mud drainage holes make cleaning and maintenance of the box more convenientRevolutionary innovation, outstanding performance, second to none, to achieve the ultimate riding experienceIt can be easily installed without modifying the rear derailleur, compatible with all SRAM 8-speed chainsRecommended use: mountain bikeGear Teeth:28 - 32TFreewheel Speed:8Components:FreewheelSensitivity:36 SoundsColour:Black + SilverMaterial:SteelPackage Contents:1* Bicycles FlywheelOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.