21x21x1 Boair 5-Stage Electrostatic Washable Ac Furnace Filter,Boair,BA-21211" /> Replaces 21x21x1 disposable air conditioner filters Electrostatic, Washable, Permanent Filter 5-Stage Electrostatic Filter Media Non-Rusting Aluminum Frame, Lifetime Warranty 40+ Sizes available - see our other listings