Register on the backside of the adapter is 2.275" to fit in the dampner with six 3/8" bolt holes on a 3.200" bolt circle. Bore in the center of the adapter is 2.00", spacer is .725" thick end to end, register on the backside is .250", step for trigger degree ring is .220" and thickness between degree ring surface and backside register step is .260" allowing the slight concave shape of the trigger ring to clear the harmonic dampner once it is installed on to the adapter.
Adapter is made from billet alum. and hard anodized for a durable finish.