Description Reviews Fermenter Kit Replacement Rubber Grommet This small rubber grommet is designed to fit the hole in our fermenter lid. The rubber creates an airtight seal around the airlock. The fermentation process requires an anaerobic environment, which means no oxygen! 1 rubber grommet creates an airtight seal fits the 12mm hole in our fermenter lid fits with a standard airlock Our Fermenter Kit comes with a rubber grommet included, but you might need a backup! Maybe you dropped it and it rolled behind the fridge...No fear! We offer the rubber grommet on its own so you don't have to throw away your kit or buy another! Looking for another silicone gasket that wraps around the outside of the fermenter lid? We offer those as well! Check out our Fermenting Guide and the EcoJarz Blog for more delicious recipes!