Carbon Activated Pre-Filter 4-pack for use with the germguardian FLT5000/FLT5111 HEPA Filter for AC5000 Series, Filter C Carbon Activated Pre-Filter will extend the life of your Air purifier by Preventing dust from flying into your filter The AF brand Pre Filters is thicker than the ones that comes with the machine, it will remove common household odors Easy to attach and sticks well Each Carbon Filter measures 4.8"x19.25" and is designed to be a direct replacement for existing Pre-Filter Made in USA from All-Filters brand material