This is a BT-50 body tube based WAC Corporal Fin can. This accurately reflects the shape of the fin cross section of the actual vehicle, a lenticular or bi-convex cross section, as well as the tapered tail cone. This 18mm engine version is based on a BT-50 airframe and of a friction fit engine mount design to preserve the scale quality for display. It will fit a BT-20 engine mount tube easily into place. It will fly wonderfully on 1/2A to C-6 power! In addition, this material is nylon, very tough for those hard rocky terrain landings. Please use this product with the understanding it is the end-users responsibility for overall safety and stability of a scratch built rocket design. This is not a replacement part or for use as a modification of any manufactured rocket kit. This is for advanced modelers with no instruction provided for engine mount assembly details, so please use at your own discretion.