We recently discovered this premium breathable silicone barrel bung and were immediately impressed with its robust design and features. To start with, the built in tabs really help make bung removal effortless. But where the bung really shines is in its 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 malolactic fermentation in barrels or tanks. 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 FE497 becomes a solid stopper!