Shimano GRX RD RX817 Di2 Rear Derailleur 1 x 11 Speed model avantm20iteam d this lightweight base layer has this lightweight base layer has been engineered by our in house fabric specialists and put through the wringer by our internal test teams so that it is able to react to your intensity of sweating and the subsequent cooling effect whatever the outside temperature It's full of compromises that let it excel at the type of riding most riders do on a daily basis The Shimano GRX 11 speed Di2 rear derailleur integrates electronic shifting with silent and uninterrupted rear operation on rough terrain An adjustable Shimano Shadow RD+ clutch prevents chain slapping and drops