Genuine Hunter F1725HE and F1725HE/21 replacement air purifier filter. Fits Hunter air purifier models HT1725. True HEPA filtration removes up to 99. 97% of airborne particles as small as 0. 3 microns in size including smoke, dust, pollen, pet hair and dander, mold spores and dust mites. Natural bamboo charcoal reduces harmful volatile organic compounds (VOCs) and household odors from cooking, cleaning, smoking and pets. Recommended to replace every 12-18 months for maximum efficiency, or more often depending on air quality & environmental factors. Package contains 1 replacement filter. Approximate Dimensions: 19-3/5 x 4-7/10 x 1-3/10 inches.