Flanders Air Filters, 20" X 25" X 1" Precisionaire Nested Glass - ( 4 Pack) New- About this item This is a standard grade furnace filter of the same type that has been protecting furnaces and central air conditioners around the world for over 50 years. The filtering medium is continuous filament spun glass. For peak equipment protection and energy efficiency, these filters should be changed monthly in periods of high use. Flanders, 20" X 25" X 1" Precisionaire Nested Glass Air Filter: Spun glass lasts up to 30 days Maximum air flow Alleviates strain on equipment

Returns accepted for this item if it's within 30 Days