Exhaust Fan Assembled Unassembled Blade Diameter 20 in Blade Material Steel Frame Material Steel For Maximum Motor Horsepower 1/2 hp For Maximum Motor Speed 1 221 RPM For Minimum Motor Horsepower 1/4 hp For Minimum Motor Speed 953 RPM Maximum Airflow 4 587 cfm Maximum Static Pressure 0.75 in wg Minimum Airflow 3 581 cfm For Cut-Out Height 22 1/2 in For Cut-Out Width 22 1/2 in For Cut-Out Diameter 22 1/2 in Guard Type None Method of Construction Stamped Number of Blades 6