The RD-RX820 is compatible with 11-34T and 11-36T 12-speed cassettes, providing a wide gear range so you can spin a comfortable cadence no matter the terrain type. The SHIMANO GRX 12-speed rear derailleur also features an integrated chain stabilizer that delivers quieter shifting and more secure chain management during rough rides. And the chain tensioner has an ON/OFF switch for outings on smooth surfaces.