The best way to be sure that you are ordering the right filter is to remove your current filter and look closely for the brand and part number or SKU. Also, check the side of the filter for the dimensions – length, height and thickness. Finally, look for an indication of the MERV rating, or efficiency, of the filter. All of these factors count when selecting the right replacement air filter for your furnace and AC system. Then, navigate to the Furnace Filters category and Refine Your Search on the left side by entering the information that you know about your current filter.