Our opinion: Electric drivetrains are the future of mountain biking. No more gears that won't shift with the new XTR Di2! Tried and tested for over four years on the road and in cyclo-cross, the Shimano DI2 electric drivetrain is the best on the market.Stability and precision!The XTR M9050GS Di2 rear derailleur provides unparalleled chain stability and precision that remains intact over time. Featuring Shadow RD+ technology, the RD-M9050 is the ultimate rear derailleur for mountain biking. Its Shadow profile is even more compact than the previous M980 series, allowing you to ride even harder on narrow, winding sections without the risk of snagging the rear derailleur. The geometry has been further optimised to ensure maximum stability, combined with interaction with the front derailleur made possible by the Synchro Shift function.- Instant response to every gear change - Smooth gear changes- Synchro Shift compatible - Synchronisation with the front derailleur - Enhanced performance in difficult conditions- E-tube electric cable transmission for stable performance - The most compact rear derailleur ever designed by Shimano- GS medium cage - Compatible with 11-speed single or double chainrings