The RD-RX815 GRX Di2 is a new electronic rear derailleur from Shimano, as part of their gravel bike specific GRX component family. Electronic shifting provides unrivalled responsiveness and when paired with the corresponding GRX components you will get an unrivalled gear shifting, gravel riding experience. All the GRX components feature additional 2.5mm clearance for the larger tyres common on gravel bikes. Key Features Adjustable chain stabilizer prevents chain slapping and drops Switch stabilizer ON/OFF to match the terrain Silent and uninterrupted rear shifting on rough terrain Di2 effortless electronic gear changes