Breathable Bung for Glass Carboys | CellarScience®

A breathable Silicone stopper that acts as both a stopper and an airlock. Unique design allows CO2 pressure to escape but keeps Oxygen and airborne contamination out. It will create a vacuum if fermenting wort cools (as opposed to pulling water in from your traditional airlock). Airtight seal is great for extended fermented lager when CO2 production is still present but very slight. The top measures 1.5" wide and the bottom is 1.125" wide. The flapper stopper protrudes roughly 2.5" above the stopper.
Fits 3, 5, 6 & 6.5 gallon glass carboys and 500 mL flasks.