1.[Perfect Compatibility] Our filters are perfectly compatible with HSP001 Smart True HEPA Air Purifier and have been tested to fit tightly with HSP001 Air Purifier. 2.[4-Stage Filter Filtration] There are 2 types of filters in the package, 2 replacement filters in total: 1 filter A and 1 filter B. (Filter A 2-in-1) One side is: Gray Cold Catalytic Filter, the other side is: Activated Carbon Filter. (Filter B 2-in-1) One side is: Blue Pre-Filter, the other side is: H13 Grade True HEPA Filter. They can effectively reduce pet dander, cooking odors, pet odors and smoke. A total of 4 stages of filtration, which can significantly improve the air quality in your room 3.[H13 Medical Grade True HEPA] In order to improve the filtration efficiency, we adopt H13 True HEPA as the replacement filter set, which can help filter 99.97% of airborne particles as small as 0.3 microns 4.[Save Money] Contains 4 sets of low-cost replacement filters. Our HSP001 filter set is designed to reduce your budget with high quality. So if you are considering which seller to buy your HSP001 air purifier from, please choose us without hesitation.