Honeywell HRF-K2 Household Odor & Gas Reducing Pre-Filter, Single Unit, Black Captures larger particles such as dust, lint, fibers & pet fur Helps absorb some Common household VOC gases & fumes Deodorizes the air, reducing odors with potassium permanganate calcite Package contains 2 pre-filters that should be replaced every 3 months Fits Honeywell air Purifier models: hfd-120-q, hfd-300 series, hfd-310 and hfd-320