Draws in fresh, cool air from the outside or exhaust stale, hot from inside. Independent draw-in and exhaust-out settings allow fan to do both simultaneously. Thermostat turns fan on and off according to a preset temperature level, plus three speeds for each fan allows the unit to adjust nicely to conditions. Designed to fit double-hung, vertical and casement windows, the fan comes with a built-in 7'' extender and two separate 3'' extenders, letting you custom fit it in windows from 24'' to 37'' wide. Lightweight plastic. Move it easily from room to room. The fans have six blades and measure 8-1/2'' in diameter. Overall, the unit is 12-1/4'' high. Fully assembled.
