Shimano 105 5500 octalink bottom bracketsplined bottom bracket designed for use with shimano road octalink crankset features oversize bb spindle large 22mm diameter chrome moly hollow pipe billet spindle reduces weight increases strength and rigidity octalink splined axlecrank arm interface results in a more rigid crank assembly compared to square tapered spindle maintenance free sealed cartridge design prevents corrosion and is easy to install aluminium adapter average weight 250ga 2 ye