It says 1800rpm but it's impossible for it to work there because it's completely, I mean completely, silent which personally I like because that's how I would use it.
I have the impression that they have set the molex to draw 5v, so either you leave it like that for silence or you remove the red one and put it on the other end for 12v so it will go 1800rpm but with noise, mind you, all this if it actually draws 5v as it is.

I bought it because my crappy case fits (80mm) in the back position to push air out.
Go ahead and buy it without fear, the price is dirt cheap, and even if you put 10 inside the case, you won't hear anything because it works out of the box at low speeds

Free & perfect!!! I have it to cool two HDDs next to them, with MOLEX please, meaning it works non-stop as soon as the PC turns on, we're talking FULL and there's not even a whisper!!! AND IT'S FREE.....

I put it on a decade-old desktop computer that had no fans at all. It is satisfactory and effective in cooling. Its materials are good, no comparison to the extreme Chinese ones. For its price, it is very good and of course, it is suitable for simple cooling and not demanding gaming. As for noise, I have 3 small fans and 1 aftermarket CPU cooler, so I can't judge which one makes noise or if it is all of them together. However, they are slightly audible within normal range and not annoying at all, even at night. Recommended for simple use.