Our extended surface rigid cell filters are designed for a wide range of HVAC applications, especially in variable-air-volume (VAV) systems. We offer efficiencies ranging from 60 percent to 95 percent, constructed with your choice of galvanized steel or wood particle board cell sides, as well as header locations of air entry side, air entry and leaving sides or no header. Rigid cell filters come in either 6” or 12” depths, as well as 4” thick minipleat filters with either beverage board or galvanized steel frames. They come in standard sizes of 12”x24”, 16”x20”, 16”x25”, 18”x24”, 20”x20”, 20”x24”, 20”x25” and 24”x24”.