Compatibility: Replacement filter kit is compatible with Austin Air Healthmate Plus FR450 Air Purifier filter. Also fits Austin Air models HM450, HM402, HM405, HM400. Each package contains (1) filter, two (2) pre-filters. Air Quality Improvement: filtration removes up to 99.97% of airborne particles as small as 0.3 microns in size including dust, smoke, pollen, pet hair and dander, mold spores and dust mites. Filtration Levels: Carbon pre-filter reduces common odors as well as gases, chemicals and VOCs (Volatile Organic Compounds) from cooking, cleaning and smoking. Particle pre-filter captures larger particles first, extending life of filter. Maintenance: Recommended to change this filter once every five (5) years under normal conditions, and more often under harsh air conditions. Approximate Measurements: Diameter: 13.5", Inner Diameter: 7.25", Height: 14.5". Filter-Monster branded replacement filter compatible with Austin Air Healthmate Plus FR450 Air Purifier filter.Package contains one (1) filter and two (2) carbon pre-filters. Engineered to fit Austin Air Healthmate Plus (HM450) Air Purifier. Also fits Austin Air models HM402, HM405, HM400.