2.6" Coupler bulkplate fits inside Phenolic 2.6 Coupler. 1/4" plywood. Fits perfectly inside PML Phenolic Couplers. (bulkhead OD 2.39") See next item...

2.6" Coupler bulkplate fits inside Rocketarium 2.6 Coupler for Bays 1/4" plywood. Bulkhead OD 2.42" See next item for other 2.6 Coupler Bulkheads

3" Coupler bulkplate fits inside 3" Coupler. 1/4" plywood.

3" Coupler bulkplate fits inside 3" Phenolic or Blue Tube Coupler. 1/4" plywood. Dimensions: - 2.858",  1/4",  16.4g

4" Coupler bulkplate fits inside 4" Coupler. 1/4" plywood. For thick wall couplers, such as Rocketarium or Madcow kraft. (bulkhead OD 3.7") See next...

4" Coupler bulkplate fits inside 4" Coupler. 1/4" plywood. For thick wall couplers, such as PML Quantum and Phenolic Couplers. (bulkhead OD 3.74")...

4" Coupler bulkplate fits inside couplers with ID 3.8". 1/4" plywood. For paper/kraft couplers, such as made by LOC, Aerotech. (OD 3.8") See previous...