Carbon Activated Pre-Filter 4-pack Compatible GermGuardian FLT4825 HEPA Filter /AC4800 Series ( Filter B ) Compatible with GermGuardian Air Purifier Models AC4800 series AC4300BPTCA, AC4900CA, AC4825, AC4850PT, PureGuardian Model AP2200CA and Black+Decker BXAP148 Carbon Activated filters extend the life of the hepa filter and remove common household odors Prevent dust & particles from getting into your main filter. Replacing your main HEPA filter is expensive so with 6 pre filters you can save both time & money. 4-Pack of Carbon Activated Pre-Filters Made in USA