The Shimano Deore XT RD-M8100/M8120 rear derailleur is designed to provide smooth and stable shifting for 12-speed MTB drivetrains. Offers fast and shockless shifting The low-profile design includes a bumper added to the derailleur pulley cage Shimano Shadow RD+ technology reduces chain slap and creates a quieter drivetrain Includes large 13t pulley Long cage is designed to be used with 1x12 drivetrain systems