The Flanders Flat Panel EZ Flow Metal Retainer is a standard grade furnace filter that works to protect furnaces and central air conditioners. The filtering medium is continuous filament spun glass that offers long-lasting durability and superior performance. The frame is made with one continuous piece of chipboard to guard against corner separation and is strengthened by a metal retainer. For peak equipment protection and energy efficiency, these filters should be changed monthly in periods of high use. This filter is effective against household dust, debris, lint and other contaminants for a cleaner, more breathable environment.