A 21x21x4 pleated air filter rated MERV 8. MERV 8 catches dust, lint, pollen and mould spores – the standard choice for a home with no particular problem. At 4 inches deep it holds far more dust than a 1-inch filter before it chokes, which is why deeper filters get changed every six to twelve months rather than every one to three.
Check the size printed on the frame of the filter you are pulling out rather than measuring the slot – nominal size and actual size differ by up to half an inch, and the printed number is the one to match. Filterbuy builds more than 600 sizes, so an odd opening is usually a stock item rather than a custom order.
Filterbuy has manufactured pleated air filters in the United States since 2013, at plants in Alabama, Pennsylvania, Texas and Utah. The company grew out of Talladega Machinery & Supply and employs around a thousand people. This filter is made in the USA.
