*** IN STOCK SHIPS TODAY *** BBC crank hub long, made from billet heat treated steel, has two .250" keyways 180 degree's apart. Uses 2.872" bolt circle and is made to work with 4-71 thru 18-71 roots or screw superchargers. This hub is for all internal balance BBC engines including 396, 402, 427, 454 and many more. Hub measures from pulley mounting surface to crank gear 2.10".