Bottles are portable containers, most often made of glass or plastics, used to hold or store liquids. They typically have narrow necks that can be closed with caps, corks, or stoppers, a geometry that aids pouring control and seal integrity. The term also covers metal containers for transporting and storing liquefied gases. In food packaging, bottle performance is judged on barrier properties against oxygen and moisture, closure seal integrity, resistance to thermal stress during hot-filling or pasteurization, and the absence of chemical migration from the container or closure into the product.