HEPA filter that captures 99.97% of allergens as small as 0.1 microns. It also contains a pre-filter/activated carbon filter layer that captures odors from cooking, pets and smoking. It is recommended to use with the GermGuardian® AC5000E, AC5250PT, AC5300B, AC5350W, AC5350B, CDAP5500; PureGuardian® AP2800CA, Black+Decker™ Model BXAP250 and Lowe's® Idlyis Model IAP-GG-125. The use of this genuine Guardian Technologies™ replacement part will maintain the product's performance. Pack of 4.