Universal Carboy Bung Drilled and Airlock - Set of 2.Carboy BungsThe universal carboy bung is designed to accommodate 3,5,6 and 6.5-gallon glass carboys. Features a lip to prevent the bung from falling too far into an orifice.Plastic 3 Piece AirlocksNecessary for most fermentation. Installs onto a carboy or bucket allowing CO2 to escape while keeping bugs out.