The 8" Electrically Reversible Twin Window Fan adds the convenience of in-window reverse and independently controlled motors, making it one of the most versatile twin window fans on the market. Independent Motor Control for Air Intake, Exhaust, or Exchange. Adjustable Thermostat for Automatic Comfort Control. Two, Whisper-Quiet Speeds. E-Z-Click Expander Panels for a Safe, Custom Fit. Fits Windows 25" to 35" Wide and 12" High and Larger. Fully Assembled for Window Use (Snap-On Feet Included for Table or Floor Use). U.L. Listed.