PRO FILTER Premium Air Filters are made of chemical resistant, high quality polyester based foam. Dual-stage design allows for superior filtration by eliminating the passage of fine dirt and dust, while helping to prevent air flow blockage. Special reticulation process offers unsurpassed air- flow and filtration. Industrial strength, resin bonded seams increase the integrity of the filters wash after wash. Packaged individually in a re-sealable bag.