This 20 x 25 x 1 disposable fiberglass filter is manufactured with high quality components. The frame is thermally bonded to the media and facing and it is constructed of continuous non respirable strands. The glass fibers are encapsulated in a polyester coating to maximize particulate retention. Safe and efficient, these fiberglass furnace filters are certified UL 900 Class 2. Excellent for use in residential furnaces and commercial equipment.