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Filterbuy 17x26x4 Air Filter MERV 13 Optimal Defense (2-Pack), Pleated HVAC AC Furnace Air Filters Replacement for Lennox x6664 (Actual Size: 16.56 x 25.94 x 4.13 Inches) - Amazon.com
16x25x5 AIRx ALLERGY Replacement for Lennox X6670 Air Filter - MERV 11, 2-Pack
Lennox X6670 MERV 11 Box Replacement Filter also for Honeywell, 16" H x 25" L x 5" W (3-Pack) - Amazon.com