Filtrete 16"x25"x1" Red Micro Allergen Defense Pleated Furnace Air Filter. This filter is 90% effective at capturing large allergens such as mold spores and pet dander, and it is electrostatically charged to capture microscopic allergens such as dust, smoke, and smog. It also captures bacteria and particles that can carry viruses, meeting the guidelines of the American Lung Association Health House Program. With a MPR rating of 1000, this filter lasts up to 3 months.