Shimano RD-TZ31 Rear Derailleurs Hanger Mount/Direct Mount pully set 6/7/8 speed 7 speed Direct Mount. Suitable for mountain bike/road bike use. Speed:6/7 speed.Suitable for 6/7 grade freewheel. Mainly used in aluminum alloy bike frame. Rd-tz 31.Bike frame with hook, please buy Direct Mount.Bike frame withouthook,please buy Hanger Mount.