Expanding Foam Polyfilla is ideal for filling and sealing awkward gaps, hollows and cavities. It shoots liquid foam deep into cavities, creating a long lasting seal, which insulates against heat, sound and moisture. Suitable for inside or out, it can be easily trimmed and sanded ready to be painted, filled or plastered. Contains a CFC – free propellant. Shoots liquid foam deep into cavities, it expands to make a long-lasting seal and insulates against head, sound and moisture. Ideal for filling and sealing awkward gaps, hollows and cavities. Can be painted over, filled or plastered.