Holmes HAWF-2041 Twin Window Fan with Comfort Control Thermostat Designed to fit into most double hung and slider windows Adjustable extender screen and bonus extender panel help to secure fan into larger windows Independent electronically reversible motors allows for air intake, exhaust, or air exchange Plug in the power cord into a 120 AC Outlet. Refer to the PDF attached below in Technical Specification for User Manual. Troubleshoot- if air does not seem to be blowing in properly adjust airflow directional switch to intake. Note-for slider windows set the fan vertically in your window opening with the left side of the fan situated on the bottom and the built-in extender panel on top Comfort control manual thermostat sets and maintains ideal comfort level Dual blade operation with independent electronically reversible motors; Three speed settings Water-resistant motors are safe to use during rainy weather; Designed to fit most double hung and slider windows Adjustable extender screen and extender panel help secure fan in larger windows; 3-year limited warranty Designed to fit windows with minimum openings of 25 in wide and 12 inches hide; With extender panels, can extend to width of 35 in.