The Glasfloss Z-Pak HC Series frame shall be a rigid construction of 26 gauge galvanized steel. A heavy gauge galvanized steel header is optional for the Z-Pak HC Series. The two distinct filtration media layers shall be a high density synthetic fiber blend. The filter media pack shall be constructed by pleating continuous sheets of media into uniform spaced pleats, which are separated and secured by flame retardant, injection molded plastic media separators. Heavy duty expanded metal shall be bonded and secured between the two layers of media. The heavy duty expanded metal shall be galvanized to resist rust and corrosion. The air entry and air exit side shall be fitted with two 26 gauge support struts. The pleated media ends are sealed and secured to the top and bottom of the metal frame to prevent air bypass. Gasket material, 3/4″ in width and 1/4″ in thickness, is optional. Glasfloss Z-Pak HC series filters shall be rated to withstand temperatures up to 180 degrees Fahrenheit. Glasfloss Z-Pak HC filters shall be Classified under U.L. std. 900.