New Formulation! UltraSeal® PF-50 Extreme Weather Straw Foam is a low expansion, one-component polyurethane foam that is UL classified and designed to be used with a straw dispenser. It is ideal for general sealing of gaps, holes and crevices in EXTREME temperature conditions all year round. UltraSeal® PF-50 is a foam system that can be used without a gun dispenser.