3M COMPANY DP02DC-4 Filtrete Filter, 20 x 20 x 4-Inch, White Filtrate high performance filters are effective at attracting and capturing 97% of large airborne allergens like pollen, mold spores, and dust mite debris Captures microscopic allergens like dust, smoke and smog particles Electrostatically charged filters Allergen Reduction Filter For Housing Units Accommodating 4" Nominal Size Filters & Is For Residential Use Lasts Up To 12 Months