Cling wrap is a thin plastic film typically used for sealing food items in containers to keep them fresh over a longer period of time. Plastic wrap, typically sold on rolls in boxes with a cutting edge, clings to many smooth surfaces and can thus remain tight over the opening of a container without adhesive or other devices. Common plastic wrap is roughly 0.5 thou, or 12.5 µm, thick. Although as technology advances the trend has been to produce thinner thicknesses, particularly for household use (as not too much stretch is needed), so now majority of brands on shelves around the world have reduced to 8, 9 or 10 microns. (source)