Model Compatibility: The Filter-Monster 4-in-1 True Replacement Air Filter is designed to be compatible with Levoit Core 300, Core 300S, and Core P350 Air Purifiers. Compatible replacement for part number Core 300-RF-WS. 4-In-1 Filtration: Included pre-filter that works with the Levoit Core 300 replacement filter to catch large debris such as hair and dust mites to extend the life of your filter. H13 Filtration: Filter replacement captures up to 99.97 percent of particles as small as 0.3 microns including smoke, dust, pollen, pet hair and dander, mold spores, and dust mites. Improve the air quality in your home all year round. Integrated Carbon: The Filter-Monster 4-in-1 Replacement Air Filter has integrated carbon that reduces household odors and VOCs (volatile organic compounds) from cooking, cleaning chemicals, and smoke. Replacement Time: Depending on air quality environment and usage, it is recommended to replace the filter every six to eight (6-8) months to help ensure the Levoit air purifier is running efficiently.