Casings and liners are thin flexible sheets, usually made of plastic or fabric, used for wrapping or lining. The films covered by this category are non-adhesive. Casings and liners are also manufactured in continuous rolls. Casing suppliers and liner suppliers conform to a variety of quality standards and are located across the United States and around the world. They differ in terms of capabilities, cost, and service.

Casing and liners include film products made from a wide variety of manufactured plastics and polymers, including polyvinyl fluoride (PVF), polyurethane, and high density polyethylene (HDPE). These film products have specific properties, including resistance to certain chemicals, high tensile strength, low permeability, and ultraviolet (UV) resistance. PVF casing or films are often used to glaze windows because they are UV-resistant, durable, and chemically-inert. A high density polyethylene (HDPE) liner also provides UV and chemical resistance, and is useful for capping landfills or lining agricultural ponds, wastewater tanks, canals, and storage tanks. Because it is resistant to many hydrocarbons, an HDPE liner is useful in hazardous or toxic environments. Polyurethane has a vast array of uses as a coating material or liner because it is waterproof and corrosion resistant. Trucks beds are often outfitted with a polyurethane liner because they are durable and easy to apply. Other casings and liners include a thermoplastic liner composed of vinyl chlorides, polyolefins, and fluoropolymers.

Casings and liners include permeable sheeting or membranes for use in filtration or reverse osmosis processes. A polymeric membrane is useful as a filter for chemical or biomedical processing applications, including micro- and nanofiltration, cell harvesting, and plasma separation. Other casings and liners are used to protect manufacturing equipment and storage tanks from wear and tear, corrosion, and static electricity. For large or heavy duty applications such as mining or construction applications, liners may be composed of ceramics or rubber.