Flanders/Precisionaire 12x20x1 Fiberglass Furnace Filters (Pack of 12) Go to amazon.com Related posts Top 13 best 20x20x1 filters flanders for 2022 FeatureFurnace filter fiberglass12x20x1 Description12" x 20" x 1", Flat Panel, EZ Flow II Spun Fiberglass Disposable Furnace Filter, No Metal Media Retainers.