SRAM Rival 1 Rear Derailleur - 11 Speed, Medium Cage, Black/SilverThe 1x specific X Horizon derailleur design provides excellent chain control and shifts well regardless of cassette size. Uses improved Type 3. 0 roller clutch design For use only with single chainring drivetrains Roller bearing clutch and parallelogram design combine to minimize chain bounce, making the drive train safer and quieter over rough terrain Not compatible with multiple chainring drive trains Item Specifications Cage Length Medium Chain