I bought this fan as I wanted to use it as an extractor on a Raspberry Pi case - I needed something small, silent and low voltage so it could be run from the Pi's USB ports.
This fan achieved all those goals and more!
It came with a USB adapter, which left the cable pretty long - too long to go a few cm into a USB port on the side of a Pi - so I cut the wires and soldered the USB connector directly on to the wires leaving the fan housing - very simple to do thanks to the nice design from Noctua and it's happily doing its job of keeping a Raspberry Pi nice and cool.
Obviously at 5v it doesn't have a lot of oomph, but for its size and how silent it is, it does move a good amount of air.
Impressed and recommended for smaller projects such as Raspberry Pi based builds!