UMLIFE 4 Pack 40mm USB Brushless Cooling Computer Fan 40mm x 10mm Fan High Performance DC 5V Cooling Fan Speed 4200 RPM Fan for Small Appliances Series Replacement

Put two on microPC on back of monitor, 80 deg F cooler but a little loud, work great and absolutely necessary!

I purchased this product when I built a Raspberry Pi case with a built-in screen with my 3D printer right away I noticed it kept getting too hot so I bought these I didn't use the USB port I wound up cutting it and hooking it to the 5 volt from the Raspberry Pi and they don't drain that much power so far the kick on I have them programmed to kick on a certain temperature they're quiet so far I've had them running about 15 hours of use. And to be honest I haven't really noticed that much battery drain so they were perfect for my robotics project. So now I pretty much use them on any electronic projects that need Cooling. And it's nice because they come with an extra long cord that you can use for USB or cut it and hook it to a 5 volt Supply very handy. I recommend

These are powerful little fans that move a lot of air for their size which makes them a little loud. That's not an issue too much for me because I bought them to help keep the temp down on my AVR and they work well, it runs about 15 to 20 degrees cooler with these in place. I fabricated a manifold out of styrofoam from the packaging of the AVR because it contours to a similar shape and size to the case. It sits on top of the case with these simply pressed into openings that I cut out of the piece. I made it so there's about an inch and a half of air space between the top of the AVR case and the bottom inside area of the styrofoam. I had to get creative with a small hand held drywall saw and it was a bit messy with the material, I switched to a finer metal reciprocating saw blade and a handle that came with the saw for holding blades for hand work and that worked better as far as keeping the mess down and was actually more precise for cutting. I used a 4 port USB hub from the USB port on the back of the AVR to plug these into, mounted on the back of the manifold. They seemed a little under powered so I did plug in the optional power cord for the USB hub into one of the ports on the power strip/surge protector behind the Home entertainment stand and that fixed that issue. When all is working it's a good set-up and keeps the temp significantly lower. They are a bit loud for their size but considering they do the job better than I had anticipated, that's a fair trade off because when the audio system is on, they aren't really noticeable unless there is a super quiet scene in a show or during the pause between songs. Definitely not a deal breaker to save life of the AVR, their worst enemy besides abuse is heat!

This usb fan came in handy to provide air circulation in my semi closed terrarium.Works well on a smart timer. Low noise and can be easily placed where needed.

These were cheap so expectations in check they work and are worth the money if you are ok with one being potentially faulty (seems I'm not the only one who got a defective fan in the bunch.)However, they are unreasonably loud for how little air they move. It's just a poor quality design - the fan blades and construction pay no effort to efficient airflow be it volumetric pressure or sound pressure. A slightly larger fan spinning at a fraction of the speed will move more air with less noise so if you can, go larger. I was installing these in Raspberry Pi cases and needed 40mm (or smaller) to cover the footprint of the case.Additionally, the USB cable is like 3 feet long, way overkill for anything you would use this for. I ended up clipping mine down and soldering the wires back together with heatshrink. Testing the fan uninstalled proved it to be quiet but after installing against a vent, the static pressure of the fan is terrible, which explains the turbulent noise.I'm going to buy one Noctua or some known brand and see if they perform better (they most likely will, but that needs to be weighed against the cost)