Cartridge BB - Forged hollow chromly spindle for ISIS Drive - Deep-groove full-complement sealed cartridge bearings - Cold forged aluminium cups - Chromoly washer-less crank bolts (M-15) - 227 Grams Not sure which one you need? Try the FSA Easy BB Tool here; http://www.fsaeasybottombrackets.com/ FSA Part Numbers 210-2658 210-2663 210-2668