SRAM X4 Rear Derailleur - 7/8/9 Speed ESP compatible (1:1 actuation ratio) for ESP trigger or twist shifters Di.R.T (Direct Route Technology) for light-effort shifting performance Alloy outer link and B-knuckle with Grilon composite P-knuckle Steel/composite cage with replaceable pulleys 7/8/9-speed compatible with top-normal resting position