: The "nominal" size is a rounded number for marketing; the "actual" size is slightly smaller to ensure a snug fit. 2. Understand MERV Ratings
The first step is checking your current filter for its (e.g., 20x25x1), which is printed on the side. what furnace filter to buy
Your lifestyle dictates the intensity of filtration you need: : The "nominal" size is a rounded number
: Uses static electricity to attract dust like a magnet. These come in disposable or washable versions. what furnace filter to buy