SHIMANO XTR RD-M9100 REAR DERAILLEURWE XT"R" SO EXCITEDShimano has been making some of the best bicycle components since the 1970's and they continue to produce some of the most sought-after components in the industry. XTR is Shimano's top-of-the-line mountain bike group and features some of the finest technology and produces an incredibly clean and reliable shift. The newest generation of XTR is not only new and shiny, it comes with all-new technology. The Shimano XTR RD-M9100 Rear Derailleur has been upgraded from 11-speed to 12-speed and has the capacity to go up to a 51 tooth cog on the rear. The RD-M9100 is designed for 1x12 drivetrains and comes in GS (short cage) and SGS (long cage). The GS will go up to a 45 tooth cog on the rear and the SGS will go up to a 51 tooth.FeaturesDesigned to work with 1x12 drivetrains and 1x11 drivetrainsGS cage goes up to a 45 tooth cog and the SGS goes up to a 51 tooth cog13 tooth pulleysinstead of 11 tooth pulleysDecreased rear derailleur tension at low gear position, to prevent high chain tension at low gearAdded bumper at rear derailleur pulley cage for silent operation | Shimano XTR RD-M9100 Rear Derailleur GS, Short Cage, 10-45 Tooth