I bought this fan to cool the processor on the Pi4. I am using a Pi4 on my 3D printer which does the job fine except the CPU overheats which slows down and stops the print job. Initially I set the fan to 3.3V and everything looked fine, but with large print jobs the CPU was still overheating. I ran it on 3.3v for a week then switched to 5v and was impressed that it was still relatively quiet. But it helped, there was no overheating. After a few days, however, I went to my printer and heard a loud buzzing noise. It turned out that the fan bearing must have failed by now, because when I tapped the case, the noise was replaced by a grinding noise. So I got the Pi4 out and made sure the fan was really broken after just a week of use. Unfortunately I waited too long to install and use it, so I have more than 30 days. Luckily it was only $10. Don't buy that, spend a few bucks more and buy a better quality fan.