This high quality Silicone Stopper gives a great airtight seal while allowing gasses to escape.
Fits 3, 5, 6 and 6.5 Gallon glass carboys and 500ml flasks. This breathable Silicone Carboy Venting Bung acts as both a solid stopper and an airlock. The unique design allows CO2 pressure to escape but keeps oxygen and airborne contamination out. During the fermentation it creates a vacuum when the beverage cools, creating less chance of oxygen exposure. The airtight seal is great for extended fermentations when CO2 production is still present but only very slightly.