Fractal Design Silent Series is a full range of silent case fans. The fans has been specifically developed to deliver sufficient airflow and still keep a low noise level. Available in sizes from 40mm up to 140mm. Delivered with 4pcs of metal screws. The electrical cable is covered with textile to make it easier to work with.
I got one of these for my PVR 5 months ago. It was fairly quiet, but not silent. This week it started being very noisy, so I've had to replace it already.
Perhaps such small fans don't have a long life. This one had replaced a Sythe Mini-Kaze which had been very quiet for 18 months, before failing noisily. I'm getting another Mini-Kaze.
Turned my Windows Home Server (that uses 3x40mm fans) into a really silent appliance. So silent, that now I can hear the HDDs spinning! Note that unlike some other (even more expensive) 40mm fans, these have 3 pin connectors, which is essential for monitoring its speed in motherboards that support it.
This fan is utter garbage, the only real reason its quite is because it does not work. you have to flick the fan to start it, then it goes, really practiable when its inside a PC Case, as soon as you shut the pc down, and restart it wont start again, unless you flick it again, do yourself a big favour and pick something else, anything else, on the plus side delivery was ok as its amazon who send it Really would not reccommend