More than just a mechanical derailleur with a battery and a motor bolted on, the XX1 Eagle AXS 12-Speed Rear Derailleur is the heart of the whole AXS system. You'll enjoy instantaneous shifts from a single touch, even under extreme chain loads during the heat of racing. It's built with a lightweight carbon fiber cage and titanium hardware that make it an ideal choice for XC riding and racing, as opposed to the enduro-focused XO1 derailleur with its forged aluminum cage. It features a shorter cage for 10mm more ground clearance than mechanical Eagle, with more chain wrap on the cassette to sit slightly further forward and further inboard from mechanical Eagle, all of which gives you more clearance against rock strikes. The Eagle AXS derailleur is also smart enough to protect itself thanks to its innovative and resilient Overload Clutch. In the event of an impact, the motor gearbox disengages, giving the derailleur freedom to move, and instantly returns back to its position while avoiding damage to the internal motor. The XX1 AXS derailleur is tested to the IP69K water and dust proofing standard so whatever race day brings, you'll be ready.