Shimano RD-RX812/RX810 GRX Shadow Plus 11 Speed Rear Derailleur Double

are characterized by quiet, precise and reliable shifting even in the most demanding terrain, RD-RX810 and RD-RX812, Smooth, The mechanical Shimano GRX rear derailleurs

This is mainly due to the Shadow RD+ chain stabilisation system which prevents the chain from slapping and dropping as well as from unnecessary movements of the derailleur's cage, thus ensuring uninterrupted shifting performance.

much like Shimanos mountain bike derailleurs., That is why an On/Off switch can be found next to the upper pulley

noise and general "chain chatter"., When activated the rear derailleur pivot takes a firm hold to reduce excessive movement