Below is a list of EPDM Gaskets manufacturers from Seattle, Washington. EPDM (ethylene propylene diene monomer) gaskets are made of a synthetic rubber that serves as a seal between two mating surfaces in machine parts. These gaskets are used as an alternative to natural rubber and other synthetic rubbers and are a prime material for waterproofing applications, as this rubber is considered to be one of the most water-resistant rubbers that exists.