A very powerful CPU cooler! You can overclock your CPU a lot without it even being warmer! Recommended for those who wants to overclock or else it would be an overkill.
A little update: currently I am running a i9-9900k at 4,7Ghz without issues. At moderate usage (playing games) I get around 50-60 degrees with a peek of 65 degrees Celsius, however when it comes to rendering it can peak at 85 degrees Celsius, with an average of 80 degrees. Nothing alarming though, if you’re not into watercooling this would do it, but if you plan on going over 5Ghz then you have to go watercooling.