Stainless SteelMade of stainless steel material, more solid and last longer, making it easier to carbonate your beverages Method of OperationWith this cap you can simply fill an old PET bottle with cold liquid of your choice and carbonate by connecting your gas ball lock disconnect. Making Soft DrinksWith it, you can make your own soda water, carbonate beer, or even make your own soft drinks. for Most PET BottlesIt is designed to fit onto most soft drink PET bottles, inject CO2 into the bottle, creating carbonation. Add and Maintain CarbonationThe carbonation cap is highly effective method to add and maintain carbonation in beverages for extended periods of time. Specification: Condition: 100%New Material: Stainless Steel Size: as shown Package Weight: Approx. 102g Package Included:1 x Carbonation