The Aerostar 20x24x1 MERV 13 pleated air filter is a replacement furnace filter for home HVAC, AC, vent, and air conditioner systems. Each filter has a nominal size of 20x24x1 and an actual size of 19.5x23.5x0.75. Measure your existing filter before ordering to confirm fit in your HVAC slot. The 4-pack provides up to months of replacement furnaces filters at the recommended 90-day change interval. MERV 13 filtration captures household dust, pollen, pet dander, mold spores, lint, fine dust, smoke particles, and some bacteria-sized particles for higher-level home air quality. The pleated design uses electrostatically charged synthetic media to attract and hold particles more effectively than flat fiberglass filters. Low airflow resistance helps maintain HVAC efficiency. The reinforced moisture-resistant frame prevents filter collapse and air bypass. Compatible with most major brands including Carrier, Bryant, Trane, Lennox, Rheem, Goodman, York, Ruud, and Honeywell furnace and air conditioner systems. Replace every 90 days under typical conditions, or every 30 days in homes with pets, smokers, or high dust levels. Made in USA.