Shimano GRX RD-RX827-SGS Di2 Wireless Rear Derailleur - 12-Speed, Long Cage, Shadow ES, BlackThe Shimano GRX RX827 Di2 Wireless rear derailleur paired with a 10 51t cassette (cassette sold separate) gives riders and racers the speed, range, and robustness to pursue any gravel challenge. With built in automatic impact recovery, an impact deflecting shape, and solid pulleys, this derailleur stands up to hard impacts and still retains its lightning quick shifting performance. Fully wireless shifting built for rough gravel terrain A wide link