RCD Corporation® Mastics are air duct sealants that save energy by sealing leaking air conditioning, heating, and HVAC air ducts in forced air heating and cooling systems. Central air conditioning and heating systems move conditioned air through air ducts. Leaks in these systems waste energy, money, and reduce indoor air quality. Repairing and sealing sheet metal ducts, flexible ducts, fiberglass duct board, and crawl spaces with RCD Corporation® adhesives, mastics, and insulation coatings improves indoor air quality, saves energy, electricity, money, and reduces carbon emissions. Professional Air Conditioning, Heating, Mechanical, and Weatherization Contractors and Technicians depend on RCD products every day.