Shimano GRX with its gravel specific ergonomics optimized gearing options rugged reliability and quiet and stable drivetrain sets itself apart from the rest of the component world 12-speed single chainset offers optimum gearing for mixed terrains and riding styles Designed to work with HollowTech II type bottom bracket cups Compatible with 12-speed HG chains Anodized aluminium crank arms Lightweight aluminium chainring 4 arm 110 mm bolt circle diameter