120251 20X25 FURNACE FILTER | The EZ Flow II filter is made to function without a retainer by adhering the frame directly to the media, which has a light skin to make it self-retaining. The EZ Flow II frame is made from heavy chipboard in a one-piece design that eliminates corner separation. Sealing is accomplished with a resilient hot-melt adhesive running the full perimeter of the frame on both upstream and downstream sides.