18x36x1 Ultra Allergen Merv 11 Pleated Replacement AC Furnace Air Filter (6 Pack) Similar to the 3M Filtrete Ultra Allergen 18x36x1 Air Filter Made in the U.S.A. Actual Size: 17 3/4 Inches (Length) x 35 3/4 Inches (Width) x 3/4 Inches (Thickness) Electrostatically-charged, pleated fabric filter media 3 Month Filter Life