Description This item is a fermentation airlock which is perfect for wine and beer fermentation. It can create a closed system that discharges carbon dioxide and prevents oxygen and harmful bacteria from getting in and it lets fermentation gas out and to keeps air from reaching the beer or wine. With one way exhaust water sealed check design, it can effectively prevent back-flush into the fermentation chamber during ambient temperature changes in the room. Feature - Color: Transparent- Material: PP- Size: 3.8 x 3.8 x 12 cm (L x W x H)- Perfect for home-brewed beer, wine, cider, pure juice fermentation and secondary fermentation.- Isolate the air from the wine/beer, discharge carbon dioxide and fermentation gas, prevent flies flying into the wine/ beer and harmful bacteria getting in.- One way exhaust water sealed check valve. Prevent back-flush into the fermentation chamber during ambient temperature changes in the room.- Easy to use. Fill water into the exhaust valve, insert to the cover of the brew barrel or rubber plug on the of the fermentation container, cover with the lid.- Standard size airlock, fit any homebrew stopper, cork, cap, plug, bung, or a grommet with a 3/8 inch hole. Warm tips: - Please use boiled water to boil and disinfect the air lock before you using it. And clean it with water after each using.- Please allow 0-1cm error due to manual measurement.Packing list: 3 x Fermentation airlock