Heat-shrink tubing is used to seal, protect, insulate and repair cable. It consists of plastic or rubber tubing that shrinks when heat is applied. Heat-shrink tubing can be made of a variety of materials including PTFE, neoprene, PVC and polyolefin. The majority of heat-shrink tubing is based on expansion. During manufacturing, the tubing is heated to near its melting point, stretched and then quickly cooled to keep the expanded shape. Upon installation, the tubing is heated to shrink it back down to its original size. Some heat-shrink tubing may have an inner layer of adhesive to provide a better seal. To fit a variety of applications, heat-shrink tubing comes in different shrink ratios that designate the amount the tubing will shrink under heat. Heating is applied using ovens, hot air guns or blowtorches and must be controlled to prevent uneven shrinkage or overheating. Heat-shrink tubing is ideal for a wide variety of applications including insulating outdoor cables against weather, protecting cable from abrasion, repairing cable splices and cable jackets and sealing connections from contaminants and moisture.