Great Stuff 20 oz Gaps & Cracks Foam Sealant. Reduce drafts and save energy with Great Stuff Gaps & Cracks Insulating Foam Sealant. This ready-to-use polyurethane insulating foam sealant expands to take the shape of gaps up to 1 (25mm) in diameter, creating a long-lasting, airtight and water-resistant seal. It is a simple, cost-effective solution to improve energy efficiency. Foam Insulation Sealant. NOTE: This product can only be shipped via Ground Shipping. Please allow extra time for delivery.