SHIMANO XT Bottom Bracket Complete bottom bracket assembly for Hollowtech II Saint M815,810,805,800-1/2/3, XT M770,771,760, Hone M600, SLX M665,661, Deore M590, and LX M580 cranks Set includes left and right hand cups, spacers, inner cover and inner O-rings (external O-rings sold separately) Sealed cups keep dirt and water out Maintenance-free design Compatible with 68mm and 73mm shells