Plenum Fan Wheel Type Backward-Curved Drive Type Belt Drive Includes Drive Package Yes Assembly Unassembled Wheel Diameter 30 1/2 in Airflow @ 0.000 in SP 19 088 cfm Airflow @ 0.250 in SP 18 818 cfm Airflow @ 0.500 in SP 18 547 cfm Airflow @ 0.750 in SP 18 276 cfm Airflow @ 1.000 in SP 18 005 cfm Airflow @ 1.250 in SP 17 731 cfm Airflow @ 1.500 in SP 17 436 cfm Airflow @ 1.75 in SP 17 141 cfm Airflow @ 2.000 in SP 16 846 cfm Airflow @ 2.500 in SP 16 193 cfm