Compatibility: Compatible with GermGuardian air purifier filters and engineered to fit FLT4825 Filter Size B. Foam gasket on the filter ensures a tight seal, preventing air from going around the sides. Measures 16.3 x 4.9 x 1.7 inches. Compatible Units: Specifically compatible with air purifier model numbers AC4300BPTCA, AC4900CA, AC4820, AC4825, AC4870, AC4825DLX AC4850PT, CDAP4500BCA, CDAP4500WCA, AP2200CA, BLACK+DECKER BXAP148. Air Quality Improvement: True HEPA 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. Filtration Levels: Carbon 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 the life of HEPA filter. Maintenance: Recommended to change this filter once every six (6) months under normal conditions, and more often under harsh air conditions. Each pack contains one (1) replacement HEPA filter and one (1) carbon pre-filter. Filter-Monster branded True HEPA replacement filter compatible with GermGuardian FLT4825 Filter Size B. Engineered to fit GermGuardian air purifier models AC4825, AC4825E, AC4825DLX, AC4300BPTCA, AC4850PT, AC4900CA, CDAP4500WCA, PureGaurdian AP2200CA, Black+Decker BXAP148. True HEPA filtraton removes up to 99.97% of airborne particles as small as 0.3 microns including dust, smoke, pollen, pet hair and dander, mold spores and dust mites. Carbon pre-filter reduces household odors from cooking and cleaning and extends the life of HEPA filter by capturing larger particles. Recommended to replace filters every 6-8 months for optimal performance. Filter-Monster branded Filter-Monster branded True HEPA replacement filter. Package contains two (2) HEPA filters with attached pre-filters.