Tier1 21 x 23 x 1 pleated air filters are constructed using electrostatically charged, 100% synthetic Kimberly Clark media which provides significantly higher particulate efficiency than regular poly/cotton media pleated air filters, with little change in static pressure. The Pleated Air Filter Panels by Tier1 capture airborne particles/allergens between 3-10 microns in size, such as particles that carry viruses and bacteria, pollen, mold spores, fine dust and pet dander. Tier1 MERV 8 filter media will not promote the growth of bacteria, mold, mildew, or fungi in normal operating environments, and has not been chemically treated. These pleated air filters are a great upgrade from standard disposable air filters! They are over 30 times more efficient at capturing microparticles than ordinary fiberglass air filters. Perfect for commercial, industrial, and residential applications, these disposable filters are the highest quality, disposable, fiberglass filters available in the market today. The Tier1 Air Filters provide equipment protection. Each Merv 8 Air Panel Filter lasts up to 3 months depending on your air quality! These air filters are environmentally friendly because the media is free of ink, dyes, resin, and contains no adhesives, binders, chemicals or additives. Use of water based adhesives containing no volatile organic compounds (VOCs), and minimum use of ink on the perimeter of the filter, make these air filters eco-friendly. This product is listed and rated by Underwriters Laboratories as U.L. Class 2. The Merv 8 air filters are comparable in performance to the 3M Filtrete Dust & Pollen: Filtrete Series. 6-pack of air filters.