Sram x1 type 21 11 speed rear mechevery detail of the 11 speed x1 x horizon rear derailleur is engineered for smooth reliable shifting actionfrom the larger upper pulley offset to the 12 tooth x sync pulley wheels 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 with cage lock technology in the rear derailleur wheel rem