This is a highly sought-after "smart-spec" build. Rear Derailleur: Shimano GRX RD-RX822-SGS (Top-tier, 12-speed, features a switchable shadow clutch, optimized for massive 10-51T climbing gears). Crankset: Shimano GRX FC-RX610 (165mm arm length—fantastic for spin clearance—with a 40T narrow-wide chainring).
