This GOOD FILTER COMPANY 1″ Air Filter / Grease Filter is made of individual layers of both flat and corrugated expanded galvanized steel and is enclosed in a heavy duty galvanized steel frame. The individual layers are in a “Criss Cross” pattern which makes these filters more efficient than other expanded metal filters. There is also at least 1 layer of filter screen in the center of these filters for added efficiency, A Good Filter Company innovation, this “criss cross” layering in the filtering media makes this air filter / grease filter more efficient and also stronger and more durable. Another Good Filter Company enhancement. The frame is heavy duty galvanized steel and is closed on one corner with a rivet on a flattened surface for more solid holding power. This 1″air filter / grease filter is made in the standard Good Filter Company tradition of hand closing the frame . Our unique construction methods, more layers of filter media, heavier duty filter media and better frame make this a better quality, more efficient and longer lasting 1″ heavy duty expanded metal filter than all others. It is an excellent air filter / grease filter for all heavy duty air and grease filtering applications. GOOD FILTER COMPANY heavy duty expanded galvanized steel filters come in 37 standard sizes and custom sizes up to 2000 square inches.