Model HRF-11. The universal True HEPA replacement filter is 99.9% effective at capturing particles such as household dust, smoke, pollen, mold spores, and cat dander. This universal filter is designed to replace Honeywall True HEPA filter model No. 20500 and 20590. Filters should be replaced every 1 to 5 years depending on use. For use with Honeywell air purifier model series: 10500, 105900, 17000, and 50100. Each model No. HRF-11 contains 1 HEPA filter and 1 gasket.