Replacement filter. Compatibility: Xiaomi Smart Air Purifier 4 Pro. Contents: 1 piece. Three-layer filter system: primary filter, high-efficiency filter, and premium activated carbon filter. Product height: 36 cm. Replace the filter every six to twelve months. Powerful all-in-one filters. A primary filter, Xiaomi's high-efficiency filter, and a premium activated carbon filter work together to purify your air and protect your health. The primary filter blocks large particles in a 360-degree range. It provides initial filtration by filtering out dust, hair, fine dust particles, and other large particles, and is resistant to wrinkling, oil, acids, alkalis, and more - ensuring a long lifespan. Xiaomi's high-efficiency filter offers 99.97% filtration of particles sized 0.3 μm. The 24,000 cm² high-efficiency filter removes PM2.5 and pollen, consistently delivering clean air. Premium activated carbon: 650,000 mg of high-quality activated carbon with its complex porous structure and evenly distributed carbon effectively removes harmful air pollutants and odors from your home.