Honeywell CF100A1009 High Efficiency Air Cleaner Filter-  16 x 25 x 4 - 2 pack MERV 8 rating-up to 20x more efficient than typical 1-Inch fiber glass filter Easily fits Aprilaire/Space-Gard models 2200 & 2250 16 x 25 x 4.5-Inch Kit Contains: 2 filters