The Shimano BB-ES300 bottom bracket is designed for use with Shimano Octalink chainsets.Key Features:Splined bottom bracket for use with Shimano Octalink chainsetsOversize BB spindle - large 22 mm diameter hollow cold forged chrome-moly pipe billet spindle reduces weight, increases strength and rigidityOctalink splined axle/crank arm interface - results in more rigid crank assembly compared to square tapered spindleSealed cartridge assembly with oversize ball bearings - maintenance-free high efficiency rubber seals keep out dirt, mud, and waterCartridge design allows easy installation without adjustment