Caliza HVAC Pack — 18x20x1 MERV 11 (6-pack)

18x20x1 MERV 11 pleated furnace filter, 6-pack. Nominal size 18×20×1; actual size is typically about 17.75×19.75×0.75 inches — measure your old filter before ordering. Aerostar filters manufactured in Orlando, FL via Factory Direct Filters. Replace about every 60–90 days under normal use.

This shows the type of filter. It may not be the exact size. Use the dimensions in the title.