1. Compatible Models: Our 400 True HEPA Replacement Filter is compatible with the 400 Air Purifier. The replacement filter has the same quality and function as the original filter to keep working at full capacity. 2. 3-in-1 Filtration: The HEPA replacement filter is made of environmentally friendly non-woven fabric and activated carbon, with a 3-stage filtration system. Fine nylon primary filter/HP 14-stage filter/activated carbon filter. 3. High-efficiency filtration system: Level 1- Filters large particles such as pet dander, hair, fiber and lint to extend filter life. Level 2- Captures 99.99% of airborne particles as small as 0.1 microns, such as household dust, pollen, etc. Level 3- Absorbs unpleasant odors in the air, such as second-hand smoke, kitchen cooking, pet odors and various odors to effectively purify the air. This fine air filtration system improves air quality and provides a comfortable air environment for your family. 4. Service life: To ensure performance, it is recommended to replace the filter every 3-6 months. According to the air conditions in your area and the frequency of use of the air purifier, ensure the filtering and purification effect. 5. After-sales service: Each filter undergoes strict quality inspection to ensure product quality.