OSI QUAD Butyl Flash flexible flashing is a rubberized butyl backed, self-adhering flashing. 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, concrete, certain types of weather resistant barriers.