American Air Filter 220-631-051 18" X 25" X 1" StrataDensity Fiberglass Air Filter (12 Pack) American Air Filter 220-631-051 18" X 25" X 1" StrataDensity Fiberglass Air Filter (12 Pack) Features: Disposable panel filters are engineered for sturdy, economical performance and ease of use Constructed with a strong, chipboard frame bonded to AAF manufactured premium grade fiberglass media Used in all types of HVAC systems to protect the coils from dirt Use as prefilters to extend the life of higher efficiency filters 18" x 25" x 1"