Hemi crank hub made from billet heat treated titanium, has two .250" keyways 180 degree's apart. Uses 2.782" bolt circle and is made to work with 6-71 thru 18-71 roots or screw superchargers. This hub is for all internal balance Hemi engines including 426, 440, KB, Bae, Tfx and many more. Hub measures from pulley mounting surface to crank gear 1.200". Hub is designed to be used with large roots or screw blowers where crank hub galling is a issue and with two unlike materials the chance of welding the crank hub on is far less. Crank hub works with all flat RCD splined degree wheels.