Fermentation Bubbler Set: The fermentation tool you will get includes 3 plastic Fermentation Bubbler with lids and 3 rubber stoppers. Enough to meet your needs and allow you to use it freely. High-Quality Materials: Our Airlock Fermentation Devices and Rubber Stoppers are made from food-grade silica gel and high-quality plastics, which are safe and non-toxic, and are good tools for food fermentation. One-way valve design: Fermentation: The one-way valve is designed to well isolate the air during secondary fermentation to avoid oxidation, and make the whole fermentation process take place automatically and discharge at room temperature without manual control. Easy to use: just install the rubber stopper with holes on the top of the receiver and the ...