The booster section has three centering rings. The forward most ring was upgraded from one 1/4" u-bolt to two 5/16" u-bolt connection points.
All centering rings were sanded to accept the larger diameter engine tube. The aft ring will hold the motor retainer. This retainer was upgraded with stainless ny-lock nuts, washers and allen cap hardened bolts.
A ring is used to strengthen the base of the rocket to help prevent damage on landing.
