Shimano es300 octalink bottom bracketsplined bottom bracket for use with shimano octalink chainsets features oversize bb spindle large 22mm diameter hollow cold forged chrome moly pipe billet spindle reduces weight increases strength and rigidity octalink splined axlecrank 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 c