The Filtrete, 20″ x 25″ x 4″, Allergen Reduction Filter, 3 Month Filter, For Housing Units Accommodating 4 ” Nominal Size Filters & Is For Residential Use, Electrostatically Charged, Attracts & Captures Particles Like Pollen, Mold Spores, & Dust Mite Debris, MPR Rating 1550, Last Up To 12 Months. Actual size: 19 3/4″ x 24 7/16″ x 4 3/16″.