This GOOD FILTER COMPANY Economy Duty electrostatic air filter is made of 2 plys of fine mesh polypropylene electrostatic filter media with a layer of self charging filter media between them and 2 outer layers of corrugated expanded aluminum. This air filter is a high quality electrostatic air filter for residential use as a furnace filter / air conditioning filter. It is enclosed in a one piece heavy duty aluminum frame with mitered corners. This Electrostatic Air Filter will outperform other residential electrostatic furnace and air conditioning air filters because it is of better quality and has more electrostatic filter material. This Electrostatic Air Filter is an excellent residential air filter but should not be used as a pre-filter for high air volume air cleaners or heavy commercial or industrial applications. The GOOD FILTER COMPANY 1″ electrostatic air filter comes in 37 standard sizes and custom sizes up to 2000 square inches.