The Xiaomi Smart Air Purifier 4 Compact Filter offers a high-quality, three-layer high-performance filtration system to protect your health. The powerful all-in-one filter cleans the air on multiple levels, resulting in significantly cleaner air. This filtration system consists of a primary filter, Xiaomi's high-efficiency filter, and a premium activated carbon filter, which work together to purify the air and keep you healthy. This replacement filter has been specifically designed for the Xiaomi Smart Air Purifier 4 Compact. The primary filter allows for 360° blockage of large particles. This is achieved through a high-efficiency filtration system that removes up to 99.97 percent of particles as small as 0.3 micrometers. Additionally, the high-efficiency filter removes PM2.5, pollen, pet dander, and other allergens.