Inside each Kit: Four-stage filtration kit includes a H13 filter, medium filter, customized germ reduction filter and activated carbon filter. 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, and more. 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. Recommended Use: Replace once (1) a year under normal conditions, or more often under harsher air quality conditions to maintain efficiency. Approximate Dimensions: 18.3 x 16.4 x 4.6 inches. Filter-Monster branded replacement compatible with MinusA2 filters remove smoke, dust, pollen, pet dander, mold spores, and dust mites from the air.