OSI Butyl Flash is a rubberized butyl backed, self-adhering 15-mil membrane. The foil backed exterior allows the flashing to be exposed to UV rays for at least 12 years. It is efficient, easy to use and provides excellent moisture and air infiltration protection around windows. It can also be used to seal doors and similar gaps and openings. OSI Butyl Flash can be easily applied in horizontal and vertical applications and will adhere to most common building substrates including vinyl, wood and concrete.