Open End Caps Molded plastisol (pvc) that seals the ends of the radial fins and acts as a gasket against the sealing plates in the filter housing. Core Support Regularly constructed of heavy perforated metal with 50% to 65% opening area, May by coated with a rust inhibitor to prevent corrosion. Media The filter element are constructed of polyester felt or polypropylene felt media rated for 10 micron at 98.9% efficiency. A variety of other materials are available upon request. The media is supported between two layers of screen to increase its strength and durability.