great stuff pro gaps and cracks - 24oz fireblock foam insulation sealant, pack of 12. closed cell, polyurethane expanding spray foam. seals & insulates gaps up to 3". applicator gun, cleaner included great stuff pro great stuff pro gaps & cracks polyurethane foam sealant is a gun-applied, insulating foam sealant that expands up to 3 inches to take the shape of gaps, creating a long-lasting, water-resistant and fireblock seal around plumbing and electrical, in basements, attics, and more.