NoctuaNF-A4x20 FLX Computer Case Fan - Cooling Components (Computer Case, Fan, 4 cm, 3700 RPM, 5000 RPM, 4400 RPM)

While not as quiet as other Noctua fans (obviously, given it's size and RPM), it's a huge improvement over other similarly specced server fans. It moves a good amount of air while maintaining a sound profile that lacks any of the whining or high-pitched hums that other 40mm fans tend to have. If you're concerned about sound and/or build quality, this is a solid pick.

I purchased an unmanaged 5 port, 10gbe / 100gbs network switch to put in my makeshift networking closet. Closet is about 6 feet from my work station. Switch works GREAT, but has a 40mm fan that is legit 40db loud on the tech sheet for it but more like 50db in real life which is like having a conversation with a person loud.To remedy the issue, I purchased this fan. The fan itself is of the high quality and acumen for brown color tones one would expect from Noctua, so I'm not even going to touch on that.What is the most amazing about this purchase is everything else it comes with the kit and how Noctua caters to the primary use case for their customers here.My OEM fan has a 2 pin connector to the PCB. Noctua includes a converter so you can splice the OEM 2 pin together with the converter that plugs into the 3 pin coming from the fan. In addition, Noctua provides 3 tool-less (mostly) connectors for the splice. When you crush them down it squirts some kind of non conductive oil into the connections to protect it from water and dust. Made by 3M, but nevertheless a WELL thought out solution to include for their customers.Running at 4000+ rpm is extremely unnecessary for this network switch & since silence is the name of the game for me a way to reduce RPM without implementing a PWM controller in my limited space configuration. Another whammy from Noctua for this problem. Two RPM cables are included that step down the rpm without the need for a separate controller. I used the ultra low noise cable. It reduce the noise some, but the fan itself made such a difference that alone should do the trick for most people.I've purchased a lot of PC components and networking hardware over the years. Not sure I've ever felt like a company thought this much about their customer for something that costs such a small amount of money. The time and frustration they saved me is immeasurable and priceless.Good job Noctua:-)

This thing is so quiet compared to the stock fan on many of my switches. The kit includes everything you need to mount it including an interface that lets you cut the wires from other switches that have unique connection. Great value for the money. It fit in my TP Link switch no problem and halved the Db rating.Noctua has a reputation for quality fans that is well deserved. Make sure to buy one that matches the voltage requirements of your product. Some use 12v headers, some use 5v. A 12v will not work on a 5v header.

I have bought lots of these over the years, and as is typical for Noctua you're getting a high quality product that is QUIET. I bought these fans to replace the ones on a network switch since I know Noctua is quieter, and while they did not work on the switch I intended them for because the switch is wired different, I used them in another one and they work perfectly.Yes some may say they don't flow as much as the industrial grade, super loud fans that come with them, but in a home environment that matters much less and I'd rather have peace and quiet thanks to Noctua.That being said, this is a small fan, small fans spin faster and are louder by nature, so I'd still recommend either using the included Low Noise Adapter Cable (labeled in the box), or implementing some sort of fan control. At 50% speed these are basically whisper quiet, and move some decent air. I also have the PWM versions of these which are easier to control for speed, but you get the idea.One small con is that the rubber dampener things that come with these are basically useless because they don't seem to stay in on the small fans. I've used them on the 120mm fans and they work fine but for these they don't really work as well and the fan slips off.