Rocketry Works
These laser cut centering rings are made from 1/8 inch birch plywood, and sized to mount a 29mm heavy wall motor tube in a 56mm (BT-70) airframe tube. The fit on the motor tube is tight, so some light sanding may be needed. Sold as a set of 2 centering...
RW-CR-29MM HW / BT-70 PW 1/8 IN