Febreze FRF101B Replacement Dual Action Filter, 1-Pack Captures up to 99% of microscopic particles, 2 microns and larger, from the air that passes through the filter For maximum efficiency, replace filter (s) every 4 months HEPA-Type filter w/ built-in odor reducing pre-filter Designed specifically for the Febreze Air Purifiers To ensure stated product performance, use only Genuine Febreze Filters