Mil-c-51278d Enables User To Drink From A Canteen While Wearing A Gas Mask Fits Standard 1-and 2-quart Military And Nato Standard 28mm Military Canteens Adapter Has A Pressure Valve Fitting Gasket Cover And A Coupling With A Self-sealing Valve Receives The Drinking Hose From Any Nato Standard Military Gas Mask Like The Msa Millennium M-40 And Mcu-2p Material: Polypropylene BPA Free Dimensions: Cap: 1.85 Inches Diameter. Cap Height: 1.36 Inches Snap Height: 2 5/8 Inches