The Shimano Deore Octalink Bottom Bracket is a splined bottom bracket for use with Shimano Octalink chainsets. Features an oversize 22 mm diameter hollow pipe billet spindle which reduces weight while increasing strength and rigidity. The Octalink splined axle/crank arm interface results in more rigid crank assembly compared to square tapered spindle. ES51 has anti-corrosion treatment inside hollow spindle which when paired with a sealed cartridge assembly creates a maintenance-free sealed cartridge keeping out dirt mud and water. Cartridge design allows easy installation without adjustment.