Shimano XT M770 HollowTech II Chainset.
The XT M770 HollowTech II Chainset is engineered for the way you ride and offers a highly versatile chainset which can suit the needs of almost all riders and is designed with HollowTech II technology which provides a high performance shifting action and the maximum sized ring is thicker and stiffer than on traditional chainsets for increased performance.
HollowTech II
The HollowTech crank set design helps reduce the overall weight by integrating the bottom bracket into the chainset which also helps improve overall rigidity. This design also allows the bottom bracket bearings to be spaced more widely which dramatically changes the loads on the bearings to increase rigidity and bearing service life.