The frame shall be made of a rigid high-density 3/4″ particleboard or 26-gauge galvanized metal. The metal frame shall have two support struts on the air-entry and air-exit sides. A 26-gauge galvanized steel header is available on the metal frame. The media shall be constructed of a water-resistant inorganic glass microfiber. For quality assurance, the glass microfiber media rolls are randomly tested and certified to meet minimum efficiency requirements by the media manufacturer. The media pack shall consist of a continuous sheet of the pleated glass microfiber. The pleated media pack is separated with multiple rolled-edge corrugated aluminum separators. The media cartridge shall be sealed with a fire retarding, rubber base, two-part sealant that bonds the media and separators to the interior of the particleboard frame filter. The media pack shall be pressure-fitted with a fiberglass media gasket on metal frame filters. A 1/4″ thick gasket shall be applied on the filter as an option. The filter shall be rated to withstand temperatures up to 180 degrees Fahrenheit. The particleboard filters and metal frame filters shall be U.L. Classified.