Ethylene propylene diene monomer, EPDM, is a synthetic elastomer. It exhibits outstanding heat, ozone, weather, and heat resistance and has excellent electrical insulating properties. EPDM is a lower-cost material than Neoprene, while offering many of the same properties. It is often used for applications that are exposed to outdoor or high-heat environments. EPDM does not have good resistance to fuels, oils and chemicals and is not recommended for use in automotive or machine applications.