The Great Stuff™ Pestblock Foam Sealant Kit, designed to block pests, also reduces unwanted airflow and improves energy efficiency all around the home. Pestblock expands to fill openings, creating long-lasting seals around plumbing and electrical penetrations, duct work, sill plates, and rim joists. It prevents unwanted critters from entering by creating a barrier and eliminating points of entry. For additional protection, Copper Mesh is included to create an even stronger barrier for rodents and critters.