Great Stuff Big Gap Filler Insulating Foam Sealant is a ready to use expanding polyurethane insulating foam sealant that fills, seals and insulates gaps up to 3 inches. The average home has a half mile of gaps and cracks where air and moisture can enter. Air sealing and insulating projects around the home can typically save homeowners up to 30% on home energy costs. Seal out energy loss and improve comfort with Great Stuff Big Gap Filler.