12 Pack 18" X 18" X 1" Disposable Flat Panel Furnace Filters Pack of Twelve design May Vary 18 X 18" X 1" Panel Filter Utilizing The Purolator" Monobond Concept of A One-piece Frame Sealed To The Media Using Heat And Pressure. Fiberglass Media Is Evenly Coated With A Gel Adhesive To Prevent Finer Particle Migration. Full Depth Loading And High Dust Holding Capacity. Filter Media Has A Skin Backing And Is Evenly Coated With A Jelled Adhesive. UL Class 2. Pack of 12