ARCTIC S4028-6K (5 Pack) - 40x40x28 mm fan, 250-6000 RPM, PWM regulated, 4-pin connector, 12 V DC - Black

Purchased to refit an old server (project on pause due to the extortionate price of electricity at the moment) - the fans are of a good quality and move a decent amount of air - I would recommend getting the high RPM fans for server use though - I'm currently using these fans in my network switches and 3D printers and have had no issues.

I needed a 40mm fan that could move some air to help cool my Tesla P4 in my home server; that card is passively cooled and designed to go in a server case with lots of air movement, so it gets really hot the second you try to run a game on it or any ML work.I 3D printed a little bracket, and screwed this fan to it then push fit it to the card; I run it at about 38% which is the power level I can't hear it at, and it still pushed enough air to keep the card cool in use.These are a little noisy when you crank them up, still not as loud as rack server fans, but you don't want them in a quiet room with you at anywhere above 40%. They're 4-pin so they're software controlled and show their RPM.Why 5 then? Well I only needed 1, but it was only a few quid more to get 5 of them compared to buying 1, and 1 fan was something like £20, so I thought I might as well get 4 spares...

I bought these to replace the fans in a Cisco switch. The exiting fans spin up to like 10K are are way overkill for what the switch actually does, plus I was adding 2 fans where the existing one had 1 fan. I figured I could get the same airflow with 2 fans running slower, therefore reducing the noise. Given how expensive Noctua are, I figured this 5 pack would be worth a shot given I have a few switches to try out.Was I correct? Well perhaps in terms of airflow, as that is one redeeming feature of the product... it's very good for the size, but the problem is that these fans are annoyingly noisy. They have a horrible whining sound, even if you reduce them below the 6k RPM that they ramp up to at max.I'm not atually sure they were less annoying that the stock fan.What is the real downside to these fans is the plastic, and the design of the shroud. It's SUPER brittle, the holes are small, and they go the full length of the fan. This means you have to use the provided screws, but the heads on them are smaller than the typical fan screw so they end up sliding through the hole.I tried using a slightly bigger screw, the plastic cracked and because the screw hole is a tube from the front to back, instead of just being a tab, it broke a huge chunk off the fan making it unusable.I now basically have £25 worth of useless fans and am going to end up with Noctua anyway...