2.1" - 1.1" (ID 54 mm - 29 mm) centering ring holds 29mm motor tube inside 54mm airframe. 1/4" plywood.
Fits into any 54mm airframe. Works best with LOC Paper, PML and GLR phenolic, Hawk Mt and Performance Rocketry fiberglass 29mm motor tube. (1.269" motor tube OD)

Please see previous item for same ring cut for different 29mm tubes.