rubber, or plastic foam. Often, an O-ring or a closure liner (gasket made of pulp or foam cap liner) is used. Linerless closures often use a deformable plastic rim or structure to maintain the seal.

Secondary seals are common with sensitive products that may deteriorate, or where extra security is needed. Foil or plastic inner seals are used on some bottles. Heat sealed lidding films are used on some tubs. External shrink bands, labels,