Really quiet, personally it didn't meet my needs because it has low airflow, but for a low-power PC it is excellent

I bought 2 fans to install them on the front of my case. I noticed that the temperatures have indeed dropped without having detailed measurements. I did have worse airflow in my old case, but now I see 71-72 degrees under full load compared to 80 before.

As for the construction, it seems very high-quality to me, and I also liked the rubber screws they provide. I hope they are also easy to remove if needed. The only negative aspect is their relatively high price. I bought them for around 17 euros each.