GREAT STUFF™ Fireblock Insulating Foam Sealant can help save much more than energy costs. Designed for residential construction, it provides an easy and effective way to maintain the continuity of an approved fire block material. GREAT STUFF™ Fireblock Insulating Foam Sealant is a minimal expansion polyurethane insulating foam sealant that fills, seals and insulates gaps up to 3/4 inch. It is specifically designed to impede the spread of fire and smoke through service penetrations. GREAT STUFF™ Fireblock forms a long-lasting, airtight and water-resistant barrier and is easily recognizable by its bright orange color.