The Box Four Rear Derailleur is the base of Prime 9 Technology that offers an affordable clutch based 1 by 8-speed derailleur that is simple and light Perfect candidate for every entry-level bike that traditionally has a 3 by drive-train that is neither durable nor user friendly For those seeking an affordable way into the world of 1x drivetrains on an otherwise entry level platform Features Box`s Limited Slip Clutch, durable nylon composite knuckle and direct channel cable stay Die cast linkage with stamped inner and outer cage *Compatible with Box Four Prime 9 drivetrain only - Not compatible with other 8 speed drivetrains