In this application a drilled and tapped head crank bolt must be used which does not have a large enough flange on the crank bolt to hold the crank hub on the engine. These new wasthers have a register for the bolt to sit in and three small relief cuts to help get the washer off the bolt if it becomes stuck to the head of the bolt.
Washer is made from heat treated steel that is .375" thick, .750" crank bolt hole, 1.950" outside diameter and black oxide finish. Crank bolt to be used with this washer is #2300-0052 or #2300-0055 which can be purchased separate by the racer if they choose.