Another note, light weight isnt always better(and with fixed gears its usually not). In bottem brackets and cranks espicailly. A lot of high end, and highly rated(by users) cranks and BBs are heavier. They are better because they are stiffer allowing all of the power generated in your legs to go directly into the movement of the bike. The only place weight is especially important on a fixed gear is in the wheels, unless you are climbing very large hills on every commute.