Great Stuff gaps and cracks insulating foam sealant with quick stop straw technology is a polyurethane-based insulating foam sealant that fills, air-seals and insulates small gaps (up to 1 in.) inside or out. What's amazing is how easy it is to use, thanks to the quick stop straw technology, and how it expands to take the shape of cracks and voids. This forms a durable, Airtight and water-resistant bond that eliminates unwanted airflow and helps reduce condensation.