The new FC-RX610-1 crank balances weight and efficiency for mixed-terrain riding. Gearing options cater for the specific demands of gravel riding and to maintain tighter gear steps for maintaining pedaling rhythm.- GRX 12 speed, 1X crankset.- Narrow-wide 38T or 40T chainring.- Gravel specific gearing ratios with 1X simplicity and wide-range gearing.- Bottom Bracket: Not included - BB-RS500/BB-RS500-PB.- Chainline: 50.1mm.