SilverStone High performance 500 rpm 1300 rpm speed range 180 mm Case Fan FM181 (Silver) High performance for positive pressure solution High air pressure and less noise with giant-bladed design 500rpm ~ 1300rpm speed range Shorting cable included for fixed speed operation Two ball Bearing Airflow at 65~150 cfm Noise level, 17dba at 500rpm and 36 dba at 1300rpm