€¢ Economically and environmentally friendly frame has a one-piece design €¢ No media retainer €¢ Fiberglass or synthetic media €¢ Available in 1€³ and 2€³ models €¢ Available in all standard sizes and custom sizes €¢ Designed for protection of furnace and central air units in residential and light commercial applications €¢ UL Classified Merv 4 Media Type: Specially formulated microfiberglass - Synthetic Max Operating Temperature: 180ËšF (82ËšC).