Direct Heat Sealers work well on many plastic materials such as coated aluminum foil, Kraft paper, Cellophane, Polypropylene, Poly-nylon and other thicker materials. It does not work with Polyethylene. The thermostat will accurately control the temperatures from 30°F to 550°F. Machines can seal material up to a total thickness of 20mil because it has upper and bottom heat elements to seal from both sides.