12 Pack Wide Mouth Mason Jar Lids for Drinking & Fermentation - Food Grade with Pre-Installed Grommets, Seals & Stoppers - Perfect for Kombucha, Pickling, Cold Brew & DIY Crafts

Without some form of gasket, the Mason jar plastic lids are not airtight. Quality Reliable Products Mason Jar Silicone Seals fit snug into Mason jar plastic lids. QRP seals provide a perfect airtight, anaerobic enclosure while fermenting Pickles, Kimchi (vegetables) or Kombucha (tea). QRP SEALS are designed wide enough that they seat firmly against the roof of any brand Mason jar plastic cap completely underneath the grooves and cannot fall out while screwing the lid onto the jar. CAUTION: OVERTIGHTENING COULD DAMAGE THE SEAL AND MAKE IT DIFFICULT TO REMOVE THE CAP! The QRP Stopper provides a "quick close" for storage when the fermentation process has ended as opposed to removing the lid and replacing with another cap, which allows too much oxygen into the jar. Metal vs. Plastic Lids use for fermentation and storage of fermented foods? We find that whatever we are fermenting doesn't normally come in contact with the lid during fermentation, however can briefly come in contact with the lid during storage. We've done the research, which reveals that metal shouldn't be used during fermentation, nor for storage of fermented foods due to possible corrosion. We use these Fermentation Lids for fermenting Kimchi, and during the second stage fermentation of Kombucha in Quart and Half Gallon Mason Jars.