The all-new Shimano Deore XT M8100 series of derailleurs brings a new level of drivetrain silence thank to decreased tension in the low gear position and an added bumper on the pulley cage. Fast and precise shifting performance optimized to take on any trailLow-profile designWide range 12-speed drivetrain with low sprocket combination -10-51TDecreased rear derailleur and chain tension in low gearNew bumper added to rear derailleur pulley cageBigger 13T pulleyYou now have the luxury of enjoying the benefits of Shimano s new wide ranging 12-speed drivetrains and this XT derailleur provides fast and precise shifting every time. Larger 13T pulleys increase efficiency and chain management while compatibility with SHIMANO's new 12-speed cassettes boosts range. They have added reinforcement to the pulley cage with a new bumper being added to help absorb all the inevitable bumps and knocks.