Spacer is made from billet alum. and is 2.750" thick with a 2.00" female register on both sides so it will run concentric off the crank hub to the starter jaw with no wobble or run out.
Spacer uses six 3/8" bolts on a 2.782" bolt circle and RBS can supply 4.00" bolts which can be purchased separate by the racer under part #400-6400.