STAGE 1 Large Particle Pre-filter. Removes particles easily seen by the naked eye (e.g. dust, hair and pet dander).STAGE 2 Medium Particle Pre-filter. Removes small to medium size particles (e.g. molds, spores and pollen).STAGE 3 30 sq. ft. of True Medical Grade HEPA. Removes 99.97% of all particles larger than 0.3 microns and 95% of all particles larger than 0.1 microns.STAGE 4 Military Grade HEGA Carbon Cloth. HEGA (High Efficiency Gas Arrestance), providing an extremely large surface area for adsorption of chemicals, gases, viruses and bacteria.Color:Black Replacement filter for the Austin Air Allergy Machine Junior. TheAustin Air Allergy Machine Junior was developed specifically for people withasthma and allergies living in smaller spaces. Its unique design increases airflow, filtering allergens from the air immediately. All junior size units areinterchangeable with all junior size filters.