This option adds the realism of the real F-15. Tougue and groove wood system, commercial 4″ air cyclinder and a smaller air cylinder add the realism to this jet. The hatch is structually stronger than a standard hatch. When you remove the hatch to start the jet, the air system, servo, and selector valve come off with the hatch. If you want this open, order it with the kit as a different exhaust tube length is used with this option.