Built-in sealed silicone gasket makes sure the jar is airtight. Automatic air release valve. After the gas is produced inside the jar, it will only to be discharged, and the external gas cannot enter the bottle. This makes doing a small batch of fermenting so easy, create your own healthy kimchi, sauerkraut and pickles. Made of BPA free sturdy glass jar, with non-slip bottom design. Two different capacity jars suitable for different need of daily life. To maintain the taste and quality of the brewed product, Besides, airtight to keep coffee, juice and more stay fresh longer. easy to disassemble and clean. Use and reuse them all year long to ferment your favorite vegetables!