Honeywell CF100A1025 4.5-Inch High Efficiency Air Cleaner Filter MERV 8 rating-up to 20x more efficient than typical 1-Inch fiber glass filter Easily fits April ire/Space-Grad models 2200 & 2251 Captures high percentage of house hold airborne particles, including microscopic particles you can't see No time consuming assembly required. Lasts up to 12-months 20 x 25 x 4.5-Inch