The fsa 386evo road ceramic bottom bracket adapts a standard 68mm bottom bracket shell to a fsa bb386evo crankset with a 30mm spindle the bottom bracket cups are made for alloy and house a bb30 bearing giving enough room to fit the 30mm spindle of the 386evo crankset the ceramic bearings will give you a 4 increase in speed over standard bearings and it is as compatible with di2 wiring