Shimano's XT level of components is iconic in the mountain biking realm, fame for pro performance and reliability at a great price point. The XT Shadow plus 12-speed rear derailleur is designed for fast, smooth and precise shifting performance optimized to take on any trail The XT RD-M8100 is made for use with Shimano 1x12 drivetrains and is suitable to use with cassettes with a low (largest) sprocket size of up to 51 teeth Genuine, brand new, boxed Shimano product - Biketart are an official UK Shimano stockist. Shadow plus features a super low profile design and optimized slant angle for super light shifting action Shadow Plus uses a chain stabilising switch that when on will reduce chain bounce in rough terrain maintaining more stable drive and shifting Single tension spring prevents contact with the chainstay resulting in a silent ride Rubber bumper on pulley cage for added silent drive 13T pulleys and decreased derailleur tension prevent high chain tension in low gears Direct cable routing prevents snagging from any trail side hazards Cold forged wide alloy links and pivot body Four fluorine-coated link pin bushings Strong return spring for a positive shifting feel Specifically designed to work with 12-speed 1x drivetrains Durable sealed 13T bearing pulleys for low friction Top normal spring uses the spring to select higher gears Max low sprocket: 51T (1x 12-speed) 41T capacity SGS cage Average weight 284g