This is a high altitude sealed helmet. When the canopy is damaged. The helmet can provide a sealed environment for the pilot's head, which can ensure the pilot to continue the mission. But it can also be used without pressure air.
If the visor is closed. The pilot can use the breather valve at the right bottom of the visor to breathe.During the first 3 days after receipt of your product. This item is in the category "Collectibles\Militaria\Vietnam (1961-75)\Original Period Items\Hats & Helmets". The seller is "felicia567" and is located in this country: CN.