16x25x1xCS, Furnace Air Filter, Purolator Key Pleat Extended Surface Air filter, Mechanical MERV 8, Actual Size 15-1/2"L x 24-1/2"H x 3/4"D by Sterling Seal & Supply, Inc (STCC) (Pack of 12). Purolator Key Pleat Air Filter, supplied by Sterling Seal & Supply is a standard capacity pleated filter, available in 1", 2" or 4" depths and several standard face sizes to accommodate most system requirements. A seven-strap die cut is located on the air-leaving side of the Key Pleat MERV 8 providing additional strength and durability to each filter. The inside of the die cut frame is coated with adhesive to ensure a solid bond at all points of contact with the media pack. The pack is sealed inside the frame and pleat tips are bonded to the stabilizers and diagonal support members. ** FACTS ABOUT HOME AND BUSINESS AIR FILTERS, ALLERGIES, AND FILTER QUALITY ** When looking to replace your air filter, there are typically two different sizes you need to understand, "Actual Size and Nominal Size". First: The Actual Size consists of the true dimensions of your filter when measuring length, width and Depth (thickness). These dimensions typically include a fraction of an inch within them. For example: 19 1/2 x 19 1/2 x 3/4 Second: What you might not realize is that filters are not sold by their actual dimensions. Instead a rounded up number is used to label filter packages. This measurement is referred to as the "Nominal Size". Third: So a filter with actual dimensions of "19 1/2 x 19 1/2 x 3/4" will have a nominal size of "20 x 20 x 1", and that will be the measurement to look for when buying your replacement filters. ** Check your air filters every month ** Heating and cooling can account for more than 50% of your home energy use. By cleaning or replacing air filters regularly, you can improve the performance of your system and reduce energy costs. Save up to $75 per year!!!