Shimano GRX RD-RX827 GRX Di2, 12-speed rear derailleur, Shadow ES, for 51T

Shimano GRX, with its gravel specific ergonomics, optimized gearing options, rugged reliability, and quiet and stable drivetrain, sets itself apart from the rest of the component world Precise and clean wireless shifting with Integrated on-board removable battery (BT-DN320 sold separately) The integrated removable on-board battery is protected within the linkage Crash recovery function, absorbs impacts and returns to its original position Connectivity BLE, ANT private Shadow ES features a super low profile skid plate design and optimized slant angle for optimal clearance Shadow ES uses a dual spring chain stabilising switch that when on will reduce chain bounce in rough terrain maintaining more stable drive and shifting The Shadow ES system is also zero maintenance and has no degradation of performance Unique structure using two springs has a tighter chain wrap that improves shifting and security with increased spring force by 70%, allowing the chain to mesh firmly with the sprocket With the tighter chain wrap skipping is prevented even as the cogs wear 13T solid pulleys and decreased derailleur tension prevent high chain tension in low gears Alloy outer and inner pulley cage saves weight and increases rigidity Cold forged wide alloy links and pivot body Fluorine-coated link pin bushings Specifically designed to work with 12-speed drivetrains 10-51 tooth compatible SGS cage