The Honeywell HRF-AP1 Universal Pre-filter helps deodorize the air as it traps larger particles such as dust, lint, fibers and pet fur.  By trapping these particles, the pre-filter helps to maximize the HEPA filter life. The activated carbon in the filter reduces common household odors from the air that passes through the filter. For best performance and to maintain freshness, the pre-filter should be replaced every 1 – 3 months, depending on your home’s environment. Each box contains 1 large pre-filter.  The perforated design makes 1 to 8 pre-filter replacements, depending on your air purifier model. Honeywell’s Universal Carbon Pre-filter fits most round Honeywell air purifiers. 1 box offers 2 replacement filters for the Honeywell QuietCare Air Purifier.