Shipped in cases of 6 only. Poly-disposable synthetic panel filters are generally used in high traffic dust laden applications and are replaced at 30-day intervals on average. filters use a progressively dense fiberglass or 100% non-woven polyester media that can be used in any application where disposable panel filters are recommended. The media material is encapsulated between two metal grids in order to maintain its shape and integrity under adverse operating conditions. The heavy-duty, one piece craft-board frame secures the media within a closed corner construction that prevents dust laden air from bypassing any filtration and maximizes its high dust holding capacity. 10 x 20 x 1