Brew Your Favourite Beverages: For Secondary Fermentation Of Home-brewed Beer Wine Cider Juice And More; It Can Be Used For Long-term Repeated Use On Fermenters Typically Up To 20 Gallons Easy To Use: Fill With Water In The Exhaust Valve Affix To The Fermenter Or To The Rubber Plug/stopper On Top Of The Fermentation Container And Cover With A Lid. Instead Of Unattractive And Poor-quality Drilled Holes In The Cap These Airlocks Release Co2 Through The Ridges Inside The Caps. Watch The Magic: The Transparent Airlock Allows You To Look Inside So You Can Watch The Airlock Do The Hard Work For You. Made Of Clear Plastic. Dimensions: Height 17cm Width 6cm Depth 2cm Package Contents: The Package Includes (2) S-shape Airlock Grommets For Home Brewing. Please Note: A Fermenter Is Required It Is Not Included