Shimano ultegra rear hub 6800the shimano ultegra series is pro proven as it is a direct trickle down from their dura ace group features high durability smooth rotation bearings easy maintenance digital adjustment system less qr axial force seriesultegra speed11 axle typeqr over locknut130mm axle length141mm flange between centers208mm34 8mma 2 year warranty is offered with all shimano products from chain reaction cycles 3 years on dura ace and xtr products buyshimano wheels