... PWM function from the motherboard Scythe KAMA PWM 120mm Cooling FanPWM Function : Fan speed is controlled automatically by the PWM function ... the PWM to automatically adjust the fan speed for you, so you get less headache!cooling fan : 1.Certification:ISO9001,UL,CE, ... TUV,ect 2.material :plastic or aluminum 3.bearing:two ball/one ball/refile Cooling Fan