One of my fans kept making this rattling noise. I installed this and the sound went away. Now silent. Thank you.

Sounds when idle on an AIO in push pull configuration is noticeable more quiet.

Noctua doesn't tell you that if you use their fans for intake, instead of exhaust, that turbulence may occur. Turbulence is poor air flow over a surface, in this case the hexagon vents on the side of my case. With the fan installed it was so loud I could hear it in games with headphones on. They don't tell you up front on their website that this problem may occur. But they will sell you a spacer to put between the fan and the intake vent to fix the problem for another ~$20 with shipping. They should tell you ahead of time so that I could not feel taken advantage of.

The M3 screws have tiny heads that will slip past Fractal Define cases' fan mounting rails, which are pretty standard. You will need washers to make the M3 screws hold onto the rails or otherwise they'll just slip right past the rails.

These spacers made my already-quiet Noctua fans even quieter and for whatever reason seem to help with air intake. Maybe the perceived better air intake is a placebo effect, but my fans definitely got quieter without a doubt.

Full disclosure, when it comes to PC stuff, I'm a bit of a Noctua fan.My setup consists of the following:- Fractal Design Meshify Mini C- i7-9700k overclocked- GTX 1660 Ti overclocked- 2x NF-A14 Intake Fans at the front- 1x NF-A14 Exhaust Fan at the rear top- 1x NF-A12x25 Exhaust Fan at the rear- 1x NF-A4x20 Exhaust Fan at the rear below the GPU- NH-U12A- Noctua Hoodie... for warming :)Noctua advertises these inlet spacers as something that could improve airflow and reduce noise depending on the application and use case. I have one of those use cases and a fond liking of every Noctua product so far. So I wanted to give these a try.In the 3 years since putting together this rig, I've had no issues with cooling or noise honestly. Prior I only had noisy gaming laptops so I don't have any other baselines. I do know that under high speeds the front intakes can be kind of noisy compared to my exhaust fans. I assume a significant cause of the noise is from the mesh sleeve in the front panel. Similar to the NF-A4x10 I have in my Raspberry Pi 4 setup, the fan is silent until it is placed in my RPi Case where it makes a lot of noise against the lid, due to that noise I run that fan at a lower voltage.Don't get me wrong, like I said I have no issues and when I game I have headphones on and my air purifier is louder anyway, but I figured I'd try them anyway. I did a very unscientific test before installing them where I tested Prime 95 Small FFT and Unigen Valley at the same time for 30 minutes (pulling 210W from the CPU and 140W from the GPU). Once I installed them I ran the same test but stopped it at 25 minutes because I thought that's what I ran the first test at... till I looked back at the screenshot, oops. I ended up with about 1*C lower average temps across some but not all CPU cores, the GPU, and System temps. That's small enough difference to be due to variation in only 1 run or the fact I didn't run the second test 5 more minutes. I should have also run the test multiple times but just wanted to install them. As for noise, from a subjective point of view I couldn't tell any difference with my fan curve. I didn't try something more realistic like gaming to see if there was a difference. So I really cannot attest to there being any improvements (or worsening) in my setup due to adding the inlet spacers.I did have one improvement. Ever since I added in the PSU Shroud on my case it was a tight fit for my front 140mm's due to the anti-vibration mounts. Removing them to add in the inlet spacers allowed them to fit without worry that I was bending the frames at all, plus the inlet spacers have their own anti-vibration mounts.I'd have to do more to test the benefit of them, which is likely not to happen at this point. I'm assuming there is some minor benefit because it does allow for some space for the fans to work but I probably either don't notice it or it is at lower speeds that it provides more benefit. I am giving Noctua the benefit of the doubt here but I'm only giving 4 stars here because I personally can't verify in my usage case that there is any actual benefit aside from the anti-vibration mounts. They are nice, and I'm keeping them in, but they aren't really doing anything significant as far as I know.

Ich benutze zwei NF-A14 in meinem Silent Base 802 in der Front. Ihre Aufgabe ist es, Frischluft für das System durch den Staubfilter und das Mesh des Silent Base zu saugen. Das machen sie auch sehr gut. Auch ohne diese Zusätze sind die Lüfter bereits sehr gut, aber die Geräuschentwicklung hat mich durchaus genervt. Tritt natürlich erst ab einer gewissen Drehzahl auf, aber es ist eben nicht die "typische" Geräuschkulisse sich drehender Lüfter, sondern vielmehr die Geräuschkulisse von Luftverwirbelungen (so ein "Wummern"). Ich habe sie trotzdem eingesetzt, weil sie mit das beste Gesamtprogramm bieten und dann halt die RPM über PWM recht niedrig gesetzt, sodass die Geräuschkulisse erst entsteht, wenn die CPU ordentlich heiß wird.Diese Teile haben das Problem tatsächlich behoben. Von den Luftwirbeln hört man nichts mehr. Das finde ich super angenehm. Gut investierte 15€. Kompliment, Noctua!