Today’s tightly built homes can trap dust, allergens and potentially hazardous contaminates. The Honeywell Home MicroDefense Air Filter CF200A1016 20x25x4 provides high-efficiency air filtration – allowing for even airflow throughout your home. It carries a MERV 12 rating which is up to 60 times more efficient than a typical one-inch fiberglass filter. This long-lasting filter can capture both microscopic particles like dust and smoke and larger contaminants like mold spores and pet dander.