Some MegaExo BBs are compatible with Shimano, so this one may work fine. (The ones for carbon chainsets are not compatible) On the otherhand Shimano BBs are so cheap you shouldn't let the fact that you already have an FSA BB influence your choice of chainset. I have bikes with MegaExo, Shimano and GXP outboard bearings and to be honest, they're all much of a muchness.