21x21x1 Lifetime Air Filter - Electrostatic Washable Permanent A/c Furnace Air Filter Replaces standard 21x21x1 sized disposable filters. Standard filters are generally undercut 3/8 inch. The actual size of this filter is 20-5/8 x 20-5/8 x 7/8 . AC FILTER USA Sold & Ships from Kilowatts Energy CENTER. All Standard filters are generally undercut 3/8 inch, Replaces disposable furnace filters, Self-charging electrostatic filter media - does not require electricity. Easy to install, easy to maintain, easy to clean with the only cleaner product recommended to maintaining youre A/C Filters lifetime warranty ASIN: - BO74S4GFTY The filter is resistant to mold and mildew. Built to last a lifetime. Easy to install, easy to maintain, because of its LOW AIR RESISTANCE dont make your Central Air Unit work harder. Reduce the number of particles such as pollen, dust, bacteria, mold, Spores and smoke. Friendly to environment. Made in USA and Imported. With a warranty satisfaction and 100% money back guarantee. These filters retail elsewhere for $ 99.99 our products manufacturing Electrostatic Filters has a rating of Merv 11.