Master Flow® Power Roof Vents are your best overall investment in attic ventilation. Our vents move the greatest volume of hot and/or humid air from your attic, saving you more in heating and cooling costs than any other type of ventilation. Available in popular colors to blend in with your roof. Heavy duty screen to deter animal, birds and insects. Every unit is factory tested prior to shipment. Large pre-punched flashing for easier installation and less chance of leaks. Adjustable Humidistat/Thermostat included for superior operation (PR2DHT and PR3DHT only). Extra long conduit for easier electrical hook-ups (PR3 models only). 120V.