Seamlessly detail rough openings, fill joints and seams, counter-flash waterproofing and air barrier components and seal around penetrations without the need for flashing tapes. Use FastFlash independently or with compatible products PROSOCO Joint & Seam Filler or PROSOCO AirDam to prevent the unwanted movement of water and air through rough openings, joints, seams and penetrations. Produces a durable, weather-tight seal. Bonds to most common building materials without priming, such as OSB, plywood, glass mat gypsum, magnesium oxide board (MgO), wood, galvanized steel, stainless steel, vinyl, polyvinyl chloride (PVC), concrete, masonry and anodized aluminum substrates. Bonds and cures in wet weather, on damp substrates, and tolerates rain immediately after application. But, also breathable allowing damp surfaces to dry. May be fully exposed to UV and weather for up to 12 months. No shrinkage. No staining. No yellowing. FastFlash is a waterproofing, adhesive and detailing compound that combines the best characteristics of silicone and polyurethane. This single-component, silyl-terminated polymer (STP) is easy to gun, spread, and tool to produce a highly durable, seamless, elastomeric flashing membrane. Use FastFlash as a liquid flashing membrane in rough openings, to fill joints and seams, to counterflash waterproofing and air barrier components in new or existing wall assemblies, and to seal around penetrations or protect countersunk fasteners.