Shimano GRX RD-RX820 Rear Derailleur - 12-Speed Direct Mount One Spec Shadow Plus Design 36t Max LowThe Shimano RD RX820 rear derailleur 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. This rear derailleur also features an integrated chain stabilizer that delivers quieter shifting and more secure chain management during rough rides. The chain tensioner has an ON OFF switch for outings on smooth surfaces. Silent and secure rear shifting on rough