3.0" - 2.1" (P) (3" - 54 mm) centering ring holds 2.1" PHENOLIC motor tube inside 3" airframe. 1/4" plywood.
Fits into any 3" airframe. Works best with PML and GLR phenolic, Hawk Mt and Performance Rocketry fiberglass 2.1" Phenolic motor tube.

Please see previous item for same ring cut for different 54 motor tubes

- 2.283", - 3.01",  0.25"