The Shimano XTR M9000 11 Speed Rear Derailleur is a Shadow Plus Dyna-Sys 11-speed rear derailleur for the ultimate in shifting performance and durability. The Direct mount gives a simpler and cleaner look and features a super low-profile design and optimized slant angle for super light shifting action. It also features a chain stabilizing switch that when on will reduce chain bounce in rough terrain maintaining more stable drive and shifting. A single tension spring prevents contact with the chain stay resulting in a silent ride and direct cable routing prevents snagging from any trail side hazards. A full carbon fiber outer pulley cage saves weight while alloy inner cage increases rigidity. The strong return spring makes for a positive shifting feel and an improved cable pull ratio provides a more accurate shift action. This derailleur is specifically designed to work with XTR M9000 11-speed Dyna-Sys 11-40T cassette and drivetrain, it is available in medium or long cage versions. The Medium cage has a 37t capacity with a maximum 10t difference on the front and maximum of a 40t for the low sprocket. For the long cage it has a 45t capacity and maximum 18t difference on the front and 40t maximum on the low sprocket.