Good cooler for its size! Really small and nice, it does a decent to good job with just one fan, on the Ryzen 3700 at idle, in Windows I have 40+. After a full load with my own code for about an hour, it reached 75-80, no more.
In general, Ryzen processors are quite aggressive in terms of speed and this is evident in the temperatures!!!
I give it three stars for its placement, which was not very good on the processor. Specifically, the heatsink has a groove where the metal that will eventually tighten with the motherboard is applied. The problem is that this metal has a lot of space and does not fit tightly! As a result, the heatsink moves slightly left and right, but very little up and down. So when the case is on the desk, the heatsink can "detach a little" from the top side due to gravity. In other words, I couldn't tighten the heatsink enough to fit perfectly, apart from a trick I did to prevent these two pieces from moving so much.

It's something you don't easily notice and I don't think I did anything wrong, it's just that the heatsink has quite loose connections. The movement that occurs is small, but you can tell that it doesn't have a good fit!

Regardless of this, I would go for a larger cooler directly, there is no reason to go for something slim other than space, to hell with beauty!

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It was installed in the Cougar MX330-X case and the i9-9900 processor. Overall, it is quite tall, like all 120mm coolers, so keep that in mind when purchasing a case if you want a large cooler. Personally, I fit it by sacrificing the position of the side fan of the case.
However, in terms of volume compared to other coolers, this one does not interfere with the RAM or any other functionality of the motherboard.
Its performance is great even though it is the smallest cooler in this series from Be Quiet. With the i9-9900 and the stock cooler, the idle temperature started at 32C - 40C, while under 95%-100% workload for a few minutes, it reached up to 80C. With the Dark Rock Slim, it never goes above 65C at 100% load (80% fan speed of the cooler), while the idle temperature is around 27C - 32C (20-25% fan speed of the cooler). I used the thermal paste included in the cooler's package.
It is silent, as I can't even tell it's there. Since I installed it a few days after setting up the computer, I can say that the noise of the case did not increase at all after its installation.
The installation gave me a little trouble, and I had to remove it and put it back on because I had installed the last component upside down.

Replacing the stock cooler on a Ryzen 5 2600. The processor is permanently overclocked to 3.9 GHz on all cores.
In idle, temperatures dropped from 28-30 degrees with the stock cooler in a room temperature of 20 degrees, to 25 degrees in a room temperature of 26 degrees, and increased to 35 degrees.
Under stress from Cinebench R23 allcore for ten minutes, temperatures dropped from 75-80 degrees with the stock cooler to 60 min - 68 max degrees depending on room temperature.
Impeccable construction, COMPLETELY silent even at 80% power.
Due to its silent operation, I have a fairly elevated fan curve, meaning it operates at 50% until reaching 45 degrees.
Clear installation instructions are provided in the package, along with thermal paste.
It was installed in a Corsair Carbide Spec-01 case with 1 120mm intake fan, 2 120mm exhaust fans on the top, and 1 120mm exhaust fan on the rear.
It was quite difficult to install, especially the fan clip from the motherboard side, but the blame is mostly on the case due to its limited space as it is a small midi case. Ideally, the motherboard should have been taken out of the case for installation, but there was no desire for such a process. Unfortunately, with this case, even though it theoretically fit according to the spec, it ultimately did not fit by a millimeter, and I had to modify the case's glass where it connects with the metal on the inside so that it doesn't touch at all.

Excellent cooler with a slim design so you won't have any issues with memory slots. With Ryzen 5 3600XT, the temperature never exceeded 71 degrees in stress tests. In idle mode, it operates at 38-42 degrees. The cooler is completely silent even at 100%! What personally won me over with this company is that when you enter their website, you can enter your motherboard model and it shows you which coolers fit, which don't, and which ones fit but take up space from the memory slots. Very useful and I recommend doing it before making a choice. Installation requires a bit of work, but if you watch the video on YouTube, you won't have any difficulties at all. It comes with thermal paste in the package, so you don't need to buy any more. Also included in the package are 2 bags with accessories and screws. One is for AMD and the other for Intel. A sign of a serious company! Finally, keep in mind that even though it's slim, it's not small! It requires a large case to fit in terms of height.

2024 update: Now being used to cool a Ryzen 9 5900x! Replaced the thermal paste with Arctic MX-4, in a Be Quiet 500DX case, with the R9 having undergone undervolting and operating at temperatures of 40-42 degrees idle and not exceeding 74 in stress tests!

Quiet, efficient, beautiful, and most importantly, not bulky in terms of the cooling it provides.
It was installed in June on a Ryzen 3600 with a Gigabyte X570 Ultra motherboard. At first, there was an amplified noise both from the cooler itself and from the motherboard's fan (Chipset), which was resolved by upgrading the BIOS to F20. After that, absolute silence in every operation!
It does not interfere with the Corsair Vengeance RGB Pro 16GB DDR4-3600MHz RAM and keeps the processor temperature very low.
It should be noted that 2 additional CoolerMaster 120mm fans that were already in the case help with airflow.
Installation on an AMD platform is easy, as only the plastic support bases need to be removed and not the back of the base, so the intermediate screws included in the case are screwed in, see instructions, and the cooler is immediately installed.
Pay attention to the placement of the fan, the metal brackets on which the fan is supported do not fit 100% inside the cooler's blades from the fan side, so do not push it.
In conclusion, the cooler is perfect, if it clicks with you aesthetically, get it without a second thought.