Presenting our beautiful External Bottom Bracket for Shimano MTB Cranksets with World Champion original ACER Racing Ceramic ball bearings. You already know of the extreme advantages of ACER Racing ceramic bearings. The lower friction and lower rolling resistance of our ceramic ball bearings result in drastic reductions is drag which translate to the equivalent of considerable static weight deductions on your bicycle allowing you to achieve higher speeds with less effort. Our External Bottom Brackets are made from forged and CNC machined alloy cups. Net weight only 83 grams. English threads 1.37"x24TPI for 68mm/73 shell. For Shimano MTB Cranksets. Available in a beautiful anodized Red .