Necro post I know, but I installed 3qty of 140mm ML fans last night in my build along with 2qty of 120mm. Very impressed so far. Low RPM as others have mentioned they very quiet, I would consider them silent and smooth as silk. I had to look in the case to make sure they were spinning. Noise performance was the #1 reason I spent a stupid amount on these fans and they nailed it. At low speed, air was still flowing nicely. Ramped up to 100%, Noise was not terrible compared to their SP performance series which made the PC sound like a hovercraft. Hurts the wallet but great fans for my specific low noise needs.