SHIMANO XTR FC-M980 Front Wheel Chainwheel Dyna-Sys gearing for greatest efficiency Hollowtech II design maximizes stiffness while keeping weight to a minimum HG-X chainring tooth profile and Dual Spike provied unparalleled assertive front shifting Precision two-piece construction for perfect chainline and chainwheel alignment Carbon/Titanium composite middle ring adds rigidity for better shifting, increases service life, and smoothly delivers power to the cassette