True HEPA filtration: HEPA filter replacement captures up to 99.97 percent of particles as small as 0.3 microns including smoke, dust, pollen, pet hair and dander, mold spores, and dust mites. Improve the air quality in your home all year round. Replacement Time: Depending on air quality environment and usage, it is recommended to replace the HEPA filter every 6 months and 3 months for the pre-filters to help ensure the Hunter HP600 Air Purifiers is running efficiently. Dimensions: The air filters approximate dimensions are 18-1/2 x 6-2/10 x 1-2/10 inches (HEPA), 18-1/2 x 6-2/10 x 1/10 inches (Pre-Filter) Model Compatibility: The Filter-Monster Filter Value Pack for Hunter Hunter HP600 Air Purifier. WHAT'S INCLUDED: Filter Monster true HEPA replacement filter package includes one (1) replacement HEPA filter and two (2) pre-filters. Filter-Monster branded replacement filter value pack compatible with Hunter air purifier models HP600. The True HEPA filter captures up to 99.97 percent of particles as small as 0.3 microns including smoke, dust, pollen, pet hair and dander, mold spores, and dust mites. This helps to ensure improved indoor air quality. To ensure effective filtration, it is recommended to replace the HEPA filter every six (6) months and or more often depending on air quality and environmental factors. Included in the package are one (1) HEPA filter and two (2) pre-filter replacement filters.