This beautiful little piece of plastic is called a twin bubble airlock. It allows CO2 gas to bubble out and it prevents unwanted air from getting in. The enclosed design also allows for slower evaporation from airlock bubbles. Plus we just like watching fermentation in action. Science! . . . #Science #Fermentation #Brewing #Bung #TwinDoubleAirlock #GreatDivideBrew #BoldCharacter #GreatMindsDrinkAlike #IndependentCraft #5280 #DenverBeer #CraftBeer #Beertography #Cheers #Instabeer #Beerme #Craftnotcrap #HappyHour #BeerLovers #Drinklocal