GermGuardian FLT5900 HEPA GENUINE Replacement Filter J is a combination filter. It includes a HEPA filter, a pre-filter/activated carbon filter layer that captures odors from cooking, pets and smoking, while helping to improve indoor air quality. The HEPA Filter captures 99.97% of dust and allergens as small as 0.1 microns such as household dust, pet dander, mold spores and plant pollens. It is recommended to use with the GermGuardian AC5900WCA. The use of this genuine Guardian Technologies replacement part will maintain the product's performance.