Pressure-sensitive adhesive tapes are generally composed of several layers: a release coating, a backing film, and an adhesive coating. The release coating is a very thin layer that prevents the tape from sticking to itself when wound on a roll. The backing film is commonly a type of polymer, such as polyethylene, polypropylene, or polyvinyl chloride, but paper and cloth tapes are also available. The type of adhesive coating used depends on the specific application of the tape, with the most common types of adhesives being natural rubber, styrenated rubber, and acrylic polymers. Packaging tape and electrical tape are the most common types of tapes that forensic scientists encounter in their work.