Lennox Healthy Climate 20" x 20" x 1" replacement furnace filters (4-pack). Merv 8 filtration in a 1-inch thick replacement filter. *Note: This product comes in a convenient 4-pack, providing you with a 1-year supply to maintain a clean, healthier home environment. This filter is an excellent choice to upgrade from the generic fiberglass filters in your local hardware store. This product is straight from the manufacturer, Lennox, one of the most respected names in home comfort and indoor air quality.