Shimano GRX Rear Derailleur RD-RX812

With an integrated chain stabilizer mechanism, the SHIMANO GRX derailleur provides a quieter experience and shifting security and precision on mixed terrain. For rides on smooth surfaces, the derailleur features and ON/OFF switch for the chain tensioner. The RD-RX812 rear derailleur is compatible with MTB cassettes with a 42T low sprocket max.