GermGuardian FLT4100 True HEPA GENUINE Replacement Filter E is a combination filter. It incorporates multiple layers of filtration including HEPA and charcoal to help improve your indoor air quality. HEPA filter captures 99% of dust and allergens, pet dander, mold spores and plant pollens. It is recommeded to use with with GermGuardian AC4100. The use of this genuine Guardian Technologies replacement part will maintain the product's performance and warranty.