- The Series 440 is 100% non-shedding organic synthetic microfiber constructed with a prefiltering media on the air entering side, and a high density synthetic fiber filter layer on the air leaving side formed into self-supporting ?V? pockets. The final filter layer is coated with Viskon-Aire® PBT-32™ Tackifier to provide a non-migrating encapsulating tackifier to ensure positive dust holding capacity. All layers are bonded together to form a progressive density laminate that will provide superior dust holding and eliminate fiber migration. The filter is constructed with a non-corrosive, welded wire frame. Each pocket will be stabilized with a non-corrosive fastener to prevent over inflation of the pocket. The wire frame shall be 11 gauge galvanized steel and be formed to have rounded corners and no sharp edges. There is to be wire frames both upstream and downstream of the media for maximum pocket support and allow the filter to be self sealing in standard holding frames.