The SRAM Red AXS E1 Rear Derailleur is the heart of the AXS ecosystem and is lighter, more efficient, and more capable than ever. Covering cassette ranges from 10-28T up to 10-36T, this wireless wonder has larger pulleys to increase drivetrain efficiency, and an Orbit fluid damper to keep everything in place over the rough stuff. One derailleur ready for 1x or 2x, on road or off.