The Lasko 8" electric twin window fan has independently controlled motors for air intake, exhaust and exchange. It has a thermostat to control the temperature. This energy-efficient Lasko reversible window fan has 2 quiet fan speeds. The expander panels provide a custom fit for windows 25" to 35" wide and 12" high. It comes fully assembled and has a patented, fused safety plug. Snap-on feet make it possible to use this dual window fan on a table or on the floor.