14x30x1, Filtrete Ultra Allergen Reduction Furance Filter Air Filter, MERV 11, by 3m 14" x 30" x 1", Purple, Ultra Allergen Filtrete Filters 3 Month Filter Is 90% Effective At Capturing Large Allergens Like Mold Spores & Pet Dander Electrostatically Charged, Captures Microscopic Allergens Like Dust, Smoke & Smog, Captures Bacteria & Particles That Can Carry Viruses Meets The Guidelines Of The American Lung Association Health House Program MPR Rating 1500, Lasts Up To 3 Months.