Shimano BB-ES300 Splined Bottom Bracket 68mm available in various different sizes. Splined bottom bracket for use with Shimano Octalink chainsets Oversize BB spindle - large 22 mm diameter hollow cold forged chrome-moly pipe billet spindle reduces weight, increases strength and rigidity Octalink splined axle/crank arm interface - results in more rigid crank assembly compared to square tapered spindle Sealed cartridge assembly with oversize ball bearings - maintenance-free high efficiency rubber seals keep out dirt, mud and water Cartridge design allows easy installation without adjustment