3M Filtrete Hoover Mach Vacuum Filter, 1 Pack Filtrete Vacuum Filters are guaranteed to be free from defects in material and workmanship Filtrete HEPA Vacuum Filters help trap 99.97% of all airborne pollutants 0.3 microns or larger, including mold spores, pet dander, grass and ragweed pollen Filtrete media contains electrostatically charged fibers that work like magnets to attract and capture particles Vacuum Filters should be replaced every 90 to 120 days for optimum performance