The SRAM X.9 Rear Derailleur features the same robust qualities and technologies as the X.0 system. If you are looking for greatness in a refined high-performance package then look no further, choose the X.9.2010 model has a lower profilePulley cage is weight-saving compositeCompatible with 7-, 8-, and 9-speed systems1:1 shifter-to-derailleur actuation ratio for precise light-action indexingMust be used with ESP shiftersAluminum upper knuckleReplaceable 11-tooth pulleys with bushingsItem SpecificationsColorSilverIntended UseMountainCassette SpacingShimano/SRAM 9Shifter/Derailleur CompatibilitySRAM 1:1Largest Cog34teethChain Wrap Capacity37teethDerailleur ActionTop-Normal (Traditional)Cage LengthMedium