Silverhook expanding foam is easy to use and is polyurethane based interior and exterior filler. Ideal for general construction and home improvement applications. Silverhook expanding foam will fill large irregular and often awkward gaps where the foam will expand to completely fill the cavity. Expanding foam is also ideal for insulation between brickwork, cladding, filling gaps around cladding, holes around pipes and cables. It can also be used with all types of sealant.