Very good fans that are quiet and punchy (for 1000U / min). Also, the speed signal is reliable The build quality is top notch and the "old-fashioned" design at the corners of the fan fits perfectly into brackets older construction. I can not tell the difference by the way to twice as expensive Bequiet SilentWings2 from noise and fan behavior.
I use 4 of these in my machine, 2 on the Prolimatech Genesis, one had replaced the Corsair PSU and as case fans. All work perfectly and without any Macke!