Easiest Mason Jar Fermentation Air Lock: These premium self-opening fermentation lids feature a one-way waterless valve that automatically vents gas when fermenting vegetables at home. This simple one-piece airlock requires no water, burps or maintenance.Foolproof fermenting accessories: Fermenting vegetables can be tricky without the right pickling supplies and equipment. Strong pressure is present and may blow off the lid or even burst the glass. Open air can spoil the fermentation, so our one-way valve prevents spoilage.Right Size & Premium Materials: The fermenter lid, 3.34 inches in diameter, is made of silicone. Robust and easy to clean. They can go into your dishwasher along with your wide mouth mason jar. The package includes 5 silicone fermentation lids, with or without 5 metal rings, depending on your choice.Low Profile Design: Our waterless plumbing system consists of a low profile cover for easier storage. Our silicone airlock valve is designed to take up less space, allowing you to conveniently store fermented vegetables in cupboards and drawers.Make probiotic-rich foods at home: Ferment your own sauerkraut, sauerkraut, sauerkraut, and more. Can ferment any vegetable, from cabbage to carrots, cucumbers, tomatoes, garlic, radishes and more. Get probiotics economically and naturally at home