Shimano RD-M9100 XTR 12-Speed Rear Derailleur, GS Medium Cage, For 10-45T/Single RingXtr shadow plus 12-speed rear derailleur for the ultimate in shifting performance and durabilityshadow plus features a super low profile design and optimized slant angle for super light shifting actionshadow plus uses a chain stabilising switch that when on will reduce chain bounce in rough terrain maintaining more stable drive and shiftingsingle tension spring prevents contact with the chainstay resulting in a silent riderubber bumper on pulley cage for added silent drive13t pulleys and decreased derailleur tension prevent high chain tension in low gearsdirect cable routing prevents snagging from any trail side hazardsfull carbon fibre outer pulley cage saves weight while alloy inner cage increases rigiditycold forged wide alloy links and pivot bodyfour fluorine-coated link pin bushingsstrong return spring for a positive shifting feelspecifically designed to work with XTR m9100 12-speed 1x drivetrains