The sram gxdh 7speed meduim cage rear derailleur the 7 speed x horizontrade rear derailleur makes shifting smooth and reliable no matter where you ride engineered to maintain consistent chain gap across all seven gears x horizontrade eliminates vertical movement for faster shifting reduced shift force and an end to ghost shifting roller bearing clutchtrade technology and the 12 tooth x synctrade pulley wheels hold the chain in place reducing bounce and chain slap and cage loc