The packaging closure is the primary interface between the product and the customer. Closures have undergone much evolution and development in recent years. The basic function of a closure is to allow easy access to a packaged product and to reclose the package, when the contents are not used fully in a single serve. However, closures are now expected to deliver a wide variety of additional functions, such as ensuring that the package has not been opened prior to the first opening by the consumer, facilitating the dispensing of the product (especially for food and pharmaceuticals) and supporting the brand equity value of the product. This volume considers the technologies relevant to packaging closures and sealing systems, structured by types of pack. It is directed at packaging technologists, those involved in the design and development of packaging and those who specify or purchase packaging.