Heat-shrink tubing is a plastic tube that is expanded during manufacture and shrinks back to original size under application of heat. This material is typically used to insulate wires and provide abrasion resistance and environmental protection for stranded and solid wire conductors, connections, joints and terminals in electrical work. Heat shrink tubing may also be used to repair insulation on wires or to bundle them together to protect wires or small parts from minor abrasion, and to create entry seals for environmental protection. Heat shrink tubing is typically made of polyolefin, which shrinks radially, but not longitudinally, when heated to between one-half and one-sixth of its supplied diameter, but a wide variety of materials are utilized in different series. Heat shrink tubing is available in a multitude of colors for color-coding of wires and connections.