TheSram XX1 11 Speed Rear Derailleur. With its “horizontal parallelogram” design and pulley offset, the SRAM XX1 11 speed rear derailleur keeps the chain gap constant across all 11 gears, providing fast, precise shifts.By limiting all movement to the horizontal axis, this design is faster, reduces shift force and eliminates ghost shifting.By eliminating unwanted chain movement, X-Horizon shifts faster, puts an end to ghost shifting and reduces shift force and chain slap. And with Cage Lock technology, wheel removal and installation are easier than ever. Sram XX1 11 Speed Rear Derailleur Features Large upper pulley offset automatically adjusts chain gap X-Horizon design reduces shift force and ghost shifting 12-tooth X-Sync pulley wheels Roller Bearing Clutch and Cage Lock technologies New silent pulley tooth design Speed: 11 Cage: Long Weight: 220g Compatibility: X-Actuation, XX1 (11 speed) Technologies: X-Actuation, X-Horizon, X-Sync, Roller Bearing Clutch, Cage Lock