Fizz Giz Growler Preservation and Repressurization Cap 3-PACK FiZZ GiZ growler preservation caps let you purge air from and repressurize the head space with pure CO after each use. Never lose another growler of fine craft beer to oxidation! Purging the head space prior to capping removes all the air and keeps your beer fresh by getting rid of the oxygen. Repressurizing the head space after capping maintains the CO level inside, ensuring no loss of carbonation. Now your finely crafted beer can have the protection it deserves. Even after opening your growler several times, the beer will remain fresh for weeks. Growler Preservation Caps fit glass and PET growlers in both the 64oz and 1-gal sizes. If you don't know how to use our caps, ask us. We'll send you a short video. It's a ten-second process.