Electronic Air Cleaner, 20X20-inch. Optimizes efficiency with airflow capturing up to 98% of particles that pass through it. It operates with all gas, oil and electric forced warm air furnaces and AC systems, and is available in four sizes to fit most ducts. Media post-filter provides enhanced filtration. Solid state power supply is self-regulating and maintains peak efficiency during a wide range of cell dirt loading conditions. Low-profile door with test button to check system operation. Helps filter efficiency-robbing "gunk" before it coats critical system parts. Very low pressure drop. Exclusive 10-year Clean Coil Guarantee. Rugged zinc-coated, roll-formed cabinet provides superior strength and corrosion protection.