Poly Wall Butyl Flash Window Flashing Tapes are used to strip in or flash straight window frames, door frames, and other construction seams. Butyl Flash is suitable for hot and cold temperatures, down to 15°F. It is a self-adhering, self-sealing flashing tape with a butyl-based waterproofing coating laminated to polyethylene film. The flashing is supplied in rolls, with an easy-to-remove film release liner, and is available in 20 mil thickness and various roll sizes.