The hub is made from billet heat treated steel, has two .250" keyways 180 degree's apart. Uses six .375" bolts on a 2.782" bolt circle and is made to work with 4-71 thru 18-71 roots or screw superchargers. Hub measures from pulley mounting surface to crank gear 1.600" and has a long nose on the front to work with an external crank support. End of crank hub is machined with a provision to drive a mandrel off the end of the crank if the racer chooses.
Degree ring is made from billet alum. black anodized then 360 degree marks are cut to allow the racer to set timing, adjust valves, etc. The degree ring measures 6.375" in dia. and can only be used with Fowler's dovetail six spline design.
RBS stocks a crank trigger degree ring for this application at an additional cost if the racer chooses #2300-0030C.