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 at 360 degrees. It provides initial filtration by filtering dust, hair, fine dust particles, and other large particles and is resistant to folding, 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, pollen, and more, 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.