1.1.(/)/[Perfectly Compatible]: Our Core 400S replacement filter is compatible with LEVOIT Core 400S Smart WiFi Air Purifi-er. Compared to Part #Core 400S -RF.Before you buy this please confirm your model first. 2.2.(/)/[In Good Quality]:Our high-quality filter element is composed of metal mesh, activated carbon particles, and plastic mesh.Our Core 400S replacement filter for levoit is designed in high-efficiency activated carbon, and fine Nylon Pre-Filter that work together for airborne particles and unwanted odors in your living space for improved air quality. 3.3.(/)/[Easy To Install]:Our Core 400S filters can be installed easily without any tools.Our package include 1 pac. 4.4.(/)/[Warm Maintenance Tip ]:To keep your LEVOIT Core 400S running at high performance, it is recommended to replace the Core 400S-RF filter every 6-8 months