True HEPA filters capture up to 99.97 percent of microscopic particles such as household dust, smoke, pollen, mold spores and pet dander. Long-life design only requires replacement every three to five years. Patented SurroundSeal Technology protects against air leakage around the filter for maximum efficiency. Stack multiple filters for larger models. Filter and included gasket are designed for use with Honeywell Air Purifiers 11520, 12520, 13520, 17200, 18150, 17400, 50150, 50200, 50250, and 50300.