2.1" - 1.1" (ID 54 mm - 29 mm) centering ring holds 29mm (S) motor tube inside 54mm airframe. 1/4" plywood.
Fits into our 54mm airframe. Works best with Estes and Rocketarium (S) Motor Tubes. (OD 1.215")

Please see other items for same ring cut for different 29mm tubes.