Shimano alivio m4000 octalink triple chainsettwo piece forged aluminium construction with a smooth and precise shifting performance due to its hyperdrive technology octalink an 8 spline interface between bottom bracket and crank arm provide better meshing and power transmission in conjunction with an octalink bottom bracket splines do not deform the crankarm therefore it is easy to remove the crank without extreme force please note bottom bracket is not included features crank constructio