Sram’s top of the line X0 drive train is on the bikes of more world class mountain bike racers than any other, and runs neck and neck with Shimano XTR when it comes to performance. The SRAM X9 system integrates all of the same world-beating technologies as X0 but without the polished jewel-like finish of X0 components. To get the absolute best performance, our X9 drivetrains use a SRAM X9 rear derailleur, front derailleur (where appropriate), shifters, cassette, and even chain.