Our Tier1 20x25x4 Air Filter MERV 11 comes in a 6-Pack. These pleated high-capacity filters are constructed using electrostatically charged filter media. This 100% synthetic material offers significantly higher particulate efficiency than typical poly/cotton media pleated filters, and captures the smallest and most troublesome airborne particles and allergens, such as particles that carry viruses and bacteria, pollen, mold spores, fine dust and pet dander. The combination of high efficiency and excellent allergen reduction make these the ideal choice for homeowners looking to improve indoor air quality.