3.0" - 2.2" (3" - 54 mm) centering ring holds 54mm 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 54mm motor tube.

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