be quiet! Silent Wings Pro 4 140mm PWM High Speed 2400 RPM Cooling Fan $24.90

be quiet! Silent Wings Pro 4 140mm PWM High Speed 2400 RPM Cooling Fan $24.90 Decent price for great performance fans that are very quiet. 3 toggle switch for speed range, M/HS/UHS. Only really start to hear sound at max output on HS, or mid output on UHS when a heap of air being pushed but very quiet performance.