Designed for barns, greenhouses, and other heavy duty applications. PSC energy efficient thermally protected motors. Flange has pre-drilled holes for easy installation. Rolled flange edges for handling protection during installation. Balanced 4-blade fan assembly totally enclosed for protection & OSHA compliance. Integrated, precision-formed exterior shutters are draft-free. Shutters open and close automatically. Housing constructed of durable 20-gauge galvanized steel. Removable interior grille. OSHA compliant grille. May be used with the adjustable thermostat with Firestat (Model No. XXADJTSTAT). 1-year limited warranty.