Ensure your equipment works its best with the AAF Flanders Nested FiberGlass MERV 1 Air Filter, measuring 20 inches by 20 inches by 1 inch. This pack includes four filters made from top-quality materials trusted for over 50 years, used to protect furnaces and central air conditioning systems globally. The filters feature a continuous filament spun glass medium that promotes optimal airflow while providing solid protection. The media is self-retaining, sticking directly to the frame, which enhances durability and resistance to wear. To maintain peak performance and energy efficiency, it is recommended to change these filters monthly.