a self-sealing, aluminum butyl membrane. It is comprised of a highperformance black butyl adhesive on a PET/AL/PET laminate film for very low vapor permeance and protection against punctures and environmental . damage. The black butyl adhesive is free of any bitumen or asphalt compounds and contains built in reinforcement for added strength. It is available in 4″ (100 mm) and 39.4″ (1.0 m) widths.