Sram Ex1, Rear Derailleur, 8Sp., Black* The EX1 derailleur capitalizes on the robust build and precise shifting attributes of the X HORIZON design, to create the worlds first derailleur specifically made for E MTBs* Engineered to handle high torque, low cadence shifting across the 11 48 tooth E BLOCK cassette* Gives E MTB riders clean, confident shifts, so they can spend more time enjoying the ride