This is the shimano dura ace 9000 36 hole rear hub elite road racers demand the best dura ace components are precision engineered for ultimate performance and durability improved freehub body design for quick pawl engagement for instant power transfer oversized axle has increased rigidity torsionally and laterally removing axle flex when under compression from the quick release thus improving rotational smoothness and durability labyrinth double contact sealing low friction seals effect