1 Pack, 2 Pack, or 4 Pack -  Brand New  Replacement Air Purifier filter for Levoit Core 350 / 300 / 300-RF / 350-RF Core 300 Air Filters Replacement, 3-in-1 filtration systems including nylon pre-filter, H13 true HEPA filter, and activated carbon filter. H13 medical grade true HEPA filter and activated carbon filter.  Core 300 Air Filters compatible with LEVOIT Core 300 air purifier and Core P350 air purifier, part number Core 300-RF & Core P350-RF.It is recommended to replace filters for every 6-8 months. The more you buy the more you save.   Free shipping within the USA only.  Any questions please ask prior to purchasing.