This breathable Silicone Stopper has a unique design that allows CO2 pressure to escape, but keeps Oxygen and airborne contaminants out. This means you can use it as both a stopper and an airlock. The benefit of this stopper over an airlock is it will not pull any liquid into your cooling wort (like an airlock can), instead it creates a vacuum. This stopper is used by numerous commercial wineries and is a favorite among homebrewers
Dimensions: 1 1/2" wide at the top and 1 1/8" wide at the bottom. Fits 3,5,6 & 6.5 Gallon glass carboys and 500ml flasks.
While the FE479 carboy stopper is a great, economical choice, you may also want to check out our premium, breathable, silicone carboy hood FE496 as well.