Compatibility: Compatible with Therapure TPP440F filters. Engineered to fit Therapure Envion air purifier models TPP440, TPP540, and TPP640. Air Quality Improvement: Filtration is rated H13 and 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. Airtight Seal: Foam gasket seal for high performance filtration directs air through the filter and keeps air from escaping around the sides. Maintenance: Recommended to change this filter once every six (6) months under normal conditions, and more often under harsh air conditions. Package contains two (2) replacement filters. Approximate Measurements: Each filter measures 17.8 x 5.25 x 2.4 inches. Filter-Monster replacement filter compatible with Therapure TPP440F filter. Engineered to fit Therapure Envion air purifier models TPP440, TPP540, and TPP640. Foam gasket seal for high-performance filtration directs air through the filter and keeps air from escaping around the sides. Recommended to replace every six (6) months for maximum efficiency, or more often in harsh environments. Contains one (1) replacement filter. Approximate Dimensions: 17.8 x 5.25 x 2.4 inches.