Built into a network part of a HP MicroServer G7 together with a S12A ULN as case fans. I had to really just look a whether the really rotates, the sound can not fix this, so quiet is! Very positive the many adapters, extensions etc. This way you can mount an exotic connector using the supplied 3M terminals. Very advantageous because the MicroServer power supply has a non-standard connector.
Although slightly more expensive but also definitely positive and only recommendable if you want to build softly computer! These were indeed my first Noctua fans but it will definitely not be the last I verbaue.