2.6" - 2.2" (2.6" - 54 mm) centering ring holds 54mm motor tube inside 2.6" airframe. 1/4" plywood.
Fits into any 2.6" airframe including BT-80 tube. Works best with PML and GLR phenolic, Madcow, Hawk Mt and Performance Rocketry fiberglass 54mm motor tube.(2.26-2.27" motor tube OD)

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