21x21x1 Electrostatic Washable Furnace A/C Gold 94% Arrestance + 1 Filter Fresh Air Filter Pads Scented Free All Standard filters are generally undercut 3/8 inch, Replaces disposable furnace filters, Self-charging electrostatic filter media - does not require electricity, Lifetime warranty The air you breathe contains many irritants such as pollen, dust, bacteria, mold spores, pet dander and smoke. Most of these particles are smaller than one micron. Our ELECTROSTATIC FILTER is an effective and efficient way to reduce the number of these particles in your air. This unique characteristic improves air flow while providing maximum filtration. Your satisfaction is 100% guaranteed or your money back in 30 days risk free trial. Lifetime Warranty Never Buy Another Filter. Electrostatic and HEPA Air Filters. We offer permanent, metal-framed Washable Electrostatic filters. We are in the Indoor Air Quality business Sold by Kilowatts Energy CENTER. MERV 6 Arrestance 82% & Merv 8 Arrestance 94% These filters retail elsewhere for $ 99.99