Fermentation Airlock S Type Twin Bubble Airlock with Grommets for Wine Beer BPA FREE Food Grade 1. Easy to use . During the fermenting process, it naturally occurring bacteria feed on the sugar and starch in the food to produce lactic acid. Fermentation helps make food easier to digest and often boosts its nutritional value. You can easily see the process. The cap don`t need the hole as the gases can escape from the gap. 2. WELL MADE - The S-shaped airlock features 2 vertical chambers connected by a sort of drain trap. It does not suck liquid back into your brew when cold crashing. It`s strong and durable. You can use it for a long time. 3. EASY TO USE - Fill the Bubbler Airlock with 1/2 or 1/3 water and insert in drilled stopper or grommet to vent gases during fermentation. It is the preferredairlock for secondary fermentation, as it is possible to monitor the pressure inside the fermenter. 4. WIDELY APPLICATION Works great for home brew with a better flavor as it lets no air in but does allow for gases to leave. It can also work for fermenting vegetables like ferment cabbage to make sauerkraut. _x000D_