This simple homebrew airlock vents carbon dioxide without allowing oxygen from entering your ferment. Remove the plastic cap and fill to the line with water, sanitizer solution, or alcohol. Insert this airlock into a rubber bung or an airlock grommet that makes any container with lid a fermentation vessel. Expertly make wine, beer, or fermented vegetable in your kitchen. Easily clean the durable plastic airlock with soap, water and (optional) brush.