I know you, because you're me. You have a shiny new radiator which came with one or more perfectly functional fans, but you're now wondering if you can get an extra two or three degrees of performance out of your machine. So you started looking into the wonderful world of fans. You now know that there are many types of fans and you figure that if you're gong to do this, you're going to do this right. So you want static pressure fans. Somehow you learned about Noctua: well-engineered, quiet fans that your favorite YouTubers rave about. They're ugly as sin, but you've come to appreciate their ugliness as a mark of exquisite Austrian quality. THESE fans are not THOSE fans. They're well-engineered, yes. But unlike their retail sisters, they come in a classy black color. And they certanly are not quiet at 3000 RPM. I agree with the guy below who said he could barely hear himself think. I have two of these mounted in push-pull on a Corsair H60 AIO radiator. Anything above 1800 is kind of annoying. Anything above 2000 RPM is obnoxious. At 3000 RPM my PC sounds like a like a Ferrarri, which is nice, but I can't imagine running them at full speed for any period of time. But let's be honest: you really shouldn't expect a static pressure fan at 3000 RPM to be "quiet." That said, at 1500 RPM the fans are pretty much silent -- comparable to the retail version. Austrian engineering wins again. Performance? They work as advertised. At full speed they move a lot of air. But if you've studied any thermodynamics you know heat transfer into moving air very quickly hits the law of diminishing returns. Put simply: more speed does not necessarily equal more heat transfer. At 1500 RPM it's about 1-2 degrees cooler than two stock fan at full speed (not bad) and is much quieter. There isn't much of a temperature improvement when ramping up to 2900 RPM, but it does get much louder (see above). So if you insist on buying these, you might as well run them at 1500 RPM. But on the other hand, if you're going to keep them below 1500 RPM at load then why bother with the server-grade iPPC version? Why not get the iPPC 2000 RPM version? Why not buy the retail version which is a couple bucks cheaper? You've already dug this far into a stack of Amazon reviews, so you're still seriously considering it. You know why and I know why. You're impressed by the numbers: THREE THOUSAND RPM. >100 CFMs. > 7 mm H2O of static pressure. 150K hour lifespan (that's 17 YEARS of continuous operation). And IP52. I'm not sure what that means but I suspect the fans will outlast the apocaylpse. Is it worth it? Probably not. But you want these fans for the same reason you installed the water cooler and for the same reason you kept adding to your overclock. You want every ounce of performance. You want every degree of coolness. You want to press your machine to the limits. You can't imagine a situation where you'd need this kind of airflow but you like knowing that it's available. You can use #6 32 1-1/4" screws to mount them to your radiator. Don't forget the washers. You're welcome. edit: Ladies and gentlemen, I am writing from the future - May 2020. The apocalypse has, in fact, come. (Perhaps it is worth mentioning that I am a resident physician, and during these trying times gaming gives me some relief.) Many parts of the machine have been upgraded in the months since my original review, but the fans remain. And they still work. Stay home. Save lives. Be sure to wash your hands.