Kwik Kut Foam Back Foam Air Filter, MERV 4, 15 x 24 x 1/4-Inch, 24-Pack Pack of 24 polyurethane foam filters ideal for window or wall air conditioners MERV 4 rating: Removes household dust, pollen, and lint Foam can easily be cut to size with household scissors Filter maintains efficiency for up to 30 days Ideal replacement for hard to find specialty filters measuring 15" x 24" or smaller