Jarden HAWF2041 Window Fan: In with the good air, out with the bad air. The Holmes Twin Window Fan operates quietly and efficiently by taking in fresh, cool outdoor air and exhausting stale, warm indoor air. The manual thermostat sets and maintains the ideal comfort level. The dual blade operation has independent controllable, reversible motors with 3 speed settings. The motors are water-resistant and are safe to use during rainy weather. Designed to fit most double hung and slider windows. 1 adjustable accordion extender screen and 1 5-inch removable panel help secure fan in larger windows. The product comes with a 3-year limited warranty.