18x18x1, NaturalAire Air Filter, MERV 8, by Flanders 18 x 18 x 1 in. NaturalAire Standard Pleated Air Filter. 100&#37; Synthetic Wire Backed Media. Clay Coated Frame&#44; MERV Rating 8&#44; 90 Day Filter. Effective Against Pollen&#44; Dust&#47;Lint&#44; Dust Mites&#44; Pet Dander&#44; Mold&#44; Bacteria&#44; Pack of 12.