Plenum Fan Wheel Type Backward-Curved Drive Type Belt Drive Includes Drive Package Yes Assembly Unassembled Wheel Diameter 18 1/2 in Airflow @ 0.000 in SP 4 472 cfm Airflow @ 0.250 in SP 4 302 cfm Airflow @ 0.500 in SP 4 132 cfm Airflow @ 0.750 in SP 3 943 cfm Airflow @ 1.000 in SP 3 731 cfm Airflow @ 1.250 in SP 3 484 cfm Airflow @ 1.500 in SP 3 211 cfm Airflow @ 1.75 in SP 2 899 cfm Airflow @ 2.000 in SP 2 500 cfm Maximum Static Pressure 2 in wc