The fermentation airlock is made of high-quality polypropylene, and the stopper is made of food-grade rubber, providing reliable support for fermenting foods. This brewing airlock can be used for preserving, wine making, beer brewing, and fermenting sauerkraut, meeting everyday fermentation needs. Simply press the stopper onto the carboy, insert the airlock into the stopper, pour water into the airlock, and cover with the lid to complete setup. The brewing airlock simplifies fermentation by effectively isolating air to prevent oxidation, allowing the fermentation process to proceed automatically at normal temperature with natural gas release. Size: Stopper: 17 x 23 x 26mm, Check valve: 17 x 1cm Color: Clear Material: Plastic Package Contents: 4 x Check valve 4 x Stopper Only the above package content is included; other items are not part of the package. Note: Lighting and display differences may cause slight variations in color between the image and the actual item. Measurement error is +/- 1-3cm.