Envelope X-RAY Spray turns opaque paper temporarily translucent, allowing the user to view the contents of an envelope without ever opening it. 30 seconds after the application, the envelope will return to its original state, leaving absolutely no markings, discoloration, or other indications of use. Each can treats several hundred square inches. Non-flammable, non-conductive, and non-photochemically reactive. Environmentally-friendly (contains no Freon). Net weight: 5 oz