AmerSeal 3-ply panel filters are designed for general air filtration in all types of industrial and commercial cooling, heating and ventilating systems. Equipped with an internal wire frame sealed inside layers of moisture resistant, polyester media, AmerSeal filters are made for dependable, trouble-free operation. They are directly interchangeable with external frame type disposable panel filters and will fit into most manufacturers' holding frames with no clips, latches, or other holding devices required. They are also excellent prefilters to higher efficiency filters.