This air filter / grease filter is made of multiple layers of both flat and corrugated expanded aluminum and is enclosed by a medium duty aluminum frame. The expanded metal layers, and there are more layers in this air filter / grease filter than in the economy duty filter, are of differing weights and diamond sizes and some are flat expanded metal and some are corrugated expanded metal, and all layers are of heavier duty material than the economy duty filter, making it more efficient that other expanded metal filters. A Good Filter Company innovation. As in the economy duty filter described above, this inconsistency in the filtering media makes this air filter / grease filter more efficient and also stronger and more durable. Another Good Filter Company filtering enhancement. The frame is medium duty aluminum and is closed on one corner with an aluminum rivet on a flattened surface for more solid holding power. This air filter / grease filter is made in the standard Good Filter Company tradition of hand closing the frame and hammering all corners for smoothness. This air filter / grease filter will perform well in light or medium duty usage for a longer period than other metal mesh filters in the standard duty class. It is an excellent filter for HVAC or air cleaner pre-filter applications, primary air filters and grease filters in commercial and residential applications.