This filter measures exactly 17-1/2 x 21 x 7/8 inches. Tired of having to remember to buy that furnace filter every 3 months? Tired of your house being dusty? Replace your disposable air filter with a washable electrostatic filter. It traps 10X more dust and allergens than cheap disposables, has a durable metal frame and comes with a lifetime warranty. Just hose off, allow to dry for 15 minutes and reinstall. Made in USA.