FSA M3 MTB BB30 Adapter Bottom BracketAlloy - For use with Ø24 MTB Alloy (with pinch bolts) MegaExo cranksets on BB30 shells. Two sizes are available to fit either 68mm (BB-CFMM3/68) or 73mm (BB-CFMM3/73) wide shells.Carbon - For use with carbon MTB MegaExo and Alloy NBD (no pinch bolt) cranksets with BB30 shells. Two sizes are available to fit either 68mm (BB-CFMM3C/68) or 73mm (BB-CFMM3C/73) wide shells. Ceramic bearings for minimum friction and maximum durability.Features: Bearings: Stainless steel ball bearings with hardened steel races (Alloy) or Ceramic bearings (Carbon) Cups: Alloy Weight: 84g (Carbon)/86g (Alloy)Buy FSA Components from Chain Reaction Cycles, the World’s Largest Online Bike Store.