This is an authentic USGI Gas Mask Canteen (NSN#8465-00-889-3744) made as part of a contract for the government by Hayes Tooling and Plastics.
This canteen is equipped with a new hydration cap, allowing you to drink from the canteen while wearing your drinking-tube equipped gas mask. You can also use it as a normal canteen by unscrewing the cap if you are not wearing a gas mask. This canteen is a great accessory for our Israeli Gas Mask.