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 axlecrank arm interface results in more rigid crank assembly compared to square tapered spindle sealed cartridge assembly with oversize ball bearings maintenance free high effic