These rely on adhesive material affixed to a backing such as paper or plastic film. Packaging with perforations in paperboard or plastic film is easy for consumers to open. This corresponded to more than of bags and plastic film being recycled in 2007 alone. Piezo elements come in the shape of ceramic discs, cylinders or a plastic film. The acetone evaporated upon bubble inflation leaving behind a solid plastic film. They often use steel pallets, steel straps with notched seals, outdoor plywood, and plastic film. Then a sheet of plastic film is stretched over the hole. Shrink wrap, also shrink film, is a material made up of polymer plastic film. The dielectric strength of class 2 ceramic and plastic film diminishes with rising frequency. It has an embedded "ghost" photo for security, covered with a plastic film. Plastic film is a thin continuous polymeric material. Evaporation is used in microfabrication, and to make macro-scale products such as metallized plastic film. However, paper absorbs moisture, and has been largely replaced by plastic film capacitors. The following example describes a typical manufacturing process flow for wound metallized plastic film capacitors. Photo identification cards and credit cards are almost always laminated with plastic film.