Bubble wrap is formed from polyethylene (LDPE) film with a shaped side bonded to a flat side to form air bubbles. Some types of bubble wrap have a lower permeation barrier film to allow longer useful life and resistance to loss of air in vacuums. The bubbles can have different diameters, to provide added levels of shock absorption during transit. Multiple layers may be needed to provide shock and vibration isolation while a single layer may simply be used as a surface protective layer. Bubble wrap is also used to form some types of mailing envelopes.