Shimano External Bearing Bottom Bracket Parts. Features: Parts for Hollowtech-II external bearing bottom brackets BB shield and o-ring seals include: 1 shield and 2 sealing o-rings SH-15500: external seal between crank arm and bearing cup Specs: Model: M960/800/760/600/580 Description: HT2 BB shield+o-rings Thread: 68/73mm Side: n/a Remarks: Also fits Saint-M800-1/2/3, XT-M760/761, Hone-M600, and LX-M580 crank/BB sets