Filtrete Ultra Allergen Reduction Filter, 20-Inch by 30-Inch by 1-Inch, 4-Pack Allergen reduction filters 90% effective at capturing large allergens like mold spores and pet dander Captures bacteria and particles that can carry viruses 90-Percentage effective at capturing particles like dust, pollen and mold spores from the air passing through the filter Carries a 1500 microparticle performance rating (mpr) Attracts and captures microscopic particles that can carry bacteria and viruses 50-Percentage better small particle filtration than our 1000 performance level filter Lasts up to 3 months