The M1 NBC Drink Tube Canteen Cap is an original USGI Army and USMC surplus item manufactured in the United States. It fits both 1 and 2 quart canteens and is designed for use in NBC (Nuclear, Biological, Chemical) environments. The cap allows the user to drink from the canteen without removing their protective mask. This product is ideal for militaria collectors or those in need of a functional canteen cap for use in hazardous environments.