18x18x1 Air Filters MERV 13 (6-Pack) by Tier1 | DiscountFilterStore
18x18x1 Merv 11 Pleated AC Furnace Filter - Case of 6 - Atomic Filters
Amazon.com: 18x18x1 Air Filter by Colorfil | Color Changing Filters Designed for Cat and Dog Odor | MERV 8 Filter | Air FIlter 18x18x1 | Air Conditioner Filter | HVAC Filter for