Austin Air FR450B Healthmate Plus Standard Replacement Filter, WhiteSTAGE 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 Over 780 cubic inches of Activated Carbon, Potassium Iodide Impregnated Carbon and Zeolite. Removes Volatile Organic Compounds (VOCs), formaldehyde, benzenes, chemicals, gases and odors. STAGE 4 60 sq. ft. of True Medical