18" x 18" x 1", Naturalaire Micro Particle Pleated Furnace Filter, Electrostatically Charged, 100% Synthetic Wire Backed Media, Clay Coated Frame, Merv Rating 10, 90 Day Filter, Effective Against Pollen, Dust/Lint, Dust Mites, Pet Dander, Mold, Bacteria, Virus Carriers, Smoke, Smog, Lead Dust.