Premium Breathable Silicone Carboy Hood the hood is designed to fit over the top of your carboy so you never have to worry about an airlock/stopper popping off. The hood has a two piece design. When set to the open position, the bung acts as an airlock and allows the release of Co2 while maintaining a seal against oxygen coming in. This makes the bung ideal for alcoholic or malolatic fermentations. When fermentation is over and you no longer want the bung to "breathe" out you just push the center cap into the bung to create a firm seal and the hood becomes a solid stopper.

Will fit all the glass carboys and most plastic carboys. Not intended for use with 1 gallon jugs