The 401 MERV 10 Air Filter helps capture and remove common airborne contaminants and allergy triggers. This replacement air filter is 6 in. thick with a large surface area for capturing pollutants and offering superior filtration to typical 1 in. filters. Filtering out airborne contaminants helps clean the air you breathe and can lower the frequency of cleaning and vacuuming by reducing dust buildup around the house. It also maximizes the lifespan of your heating and cooling systems, which can become inefficient with dust and particle buildup. This genuine AprilAire 401 Air Filter Replacement is rated MERV 10. The 401 filtering media is a surface-loading filter. This means that its efficiency increases with usage. The 401 Filter can last up to 2 years. If you run your HVAC system fan all day, every day, replace it after 12 months. It's easy to swap out thanks to the new and improved ribbon design that holds the pleats to the proper spacing. Contaminants removed based on air passing through the filtering system, Performance tested to ASHRAE 52.2, Standard, minimum efficiency reporting value - MERV 10.