HQRP 2-Pack True HEPA Filter B for GermGuardian FLT4825 / FLT4850PT / FLT22CB4 Replacement Coaster HQRP&reg; 2-pack True HEPA Replacement Filter Size B plus HQRP&reg; Coaster; Multiple levels of cleaning include HEPA, Pre-Filter / Activated Carbon Filter to help improve indoor air quality; The filter has met True-HEPA standards (retains 99.97% of 0.3 microns which pass through the filter); Combination filter needs to be replaced every 6-8 months depending on the use of the product; Compatible with Original filter; Easy to install; 2 weeks DOA replacement warranty!