Filtrete's 16"x25"x4" Allergen Reduction Filter is electrostatically charged to attract and capture particles like pollen, mold spores, and dust mite debris. With an MPR rating of 1550, it effectively filters out harmful particles and lasts up to 12 months. This filter is designed for residential use and fits housing units accommodating 4" nominal size filters. It measures 15 3/4"x24 7/16"x4 3/16" in actual size.