Poly-coated fiberglass air filters are designed to fit CellarPro VS Series cooling units. These filters are for interior use only. Poly-coated fiberglass air filters trap more dust particles than regular fiberglass filters. The frame is made of fiber-board and has two tin-plated steel grills (bonded to each side) as well as sealed corners to prevent dust leakage. Filters are marked with airflow direction. Filters meet UL Class 2 flame retardant requirements. Maximum temperature is 180 degrees.