Filter King Merv 8 18x18x2 4-Pack Air Filter actual size is 17.5x17.5x1.75. Our 18x18x2 Furnace Filters are designed to last up to 90 days. These pleated 2-inch air filters are ideal for maintaining the efficiency of your heating and cooling systems. Make sure you measure your filter. The actual size of this pleated Merv 8 filter is 17-1/2 x 17-1/2 x 1-3/4