Almost identical to the previous incarnation of SRAM's original X01 rear derailleur, the SRAM X01 2. 1 Rear Derailleur features small improvements to the original, giving you smooth, precise shifting and ultra reliable performance with your SRAM 1x11 drivetrain. Its X Horizon design ensures steady horizontal chain movement, eliminating ghost shifting from your trail rides. Loaded with industry leading technologies, the rear derailleur's Roller Bearing Clutch, which reduces chain slap and bounce, keeps the bike nice and quiet over the roughest stretches of trail. Its Cage Lock technology offers fast, simple wheel removal and installation, thanks to its convenient locking mechanism. Simply push the derailleur's cage forward, lock it into place with the push of a tab, and freely work on your bike without the derailleur getting in your way. Please note that the X01 2. 1 Rear Derailleur is only compatible with SRAM 11 speed XX1, X01, and X1 drivetrains.