The Hollowtech II crank and bottom bracket combines race proven hollow forging technology with the integrated crankset bottom bracket. Weight is reduced while rigidity power transfer is radically increased. In addition to Hollowtech II integrated design the crank arms are hollow which provide amazing strength and rigidity at a light weight. Finally, SG X chainrings enable super smooth front shifting. Special tooth profiles, pick up spikes and ramps help make the front derailleur shifts quiet, easy and trouble free for you the rider.