Filtrete 14"x25"x1" Red Micro Allergen Defense Pleated Furnace Air Filter. It is 90% effective at capturing large allergens like mold spores & pet dander. Electrostatically charged, it traps microscopic allergens like dust, smoke & smog, including bacteria & particles that can carry viruses. Meeting the guidelines of the American Lung Association Health House Program, this filter has a MPR rating of 1000 and lasts up to 3 months.