This expanded metal pre-filter is made of multiple layers of expanded aluminum and aluminum filter screen, enclosed in a heavy duty aluminum frame and secured on one corner with an aluminum rivet. This expanded metal pre-filter is not as efficient as the bonded aluminum mesh filter, but it is nearly indestructible. It is an extra heavy duty pre-filter that can be used for various filtering applications including primary filters and pre-filters. The frame is mechanically closed so it grips the filter media more securely and mechanical closing also removes any sharp edges in the corner areas. The heavy duty aluminum frame has rounded edges so it won’t split like most of the light duty sharp edged filters. The frame is closed on one corner by an aluminum rivet, not a thin metal tab that can break like other pre-filters. This is a very strong, rigid durable filter. It will perform well for extended periods under heavy use. It is recommended for medium and heavy air volumes in industrial and commercial type applications.