Mac Mini 2018 Fan Mount

The fan is a SilverStone SST-AP182 with a hole distance of 165mm along the sides of the square hole pattern.

With the fan on top of the Mac Mini, the metal metal enclosure runs about 10 degrees Celsius cooler than without, as measured by iStat Menus. And that is with the lowest speed setting of the fan (500rpm, 102m³/​h, 17dB).

Only disadvantage: you cannot press the power button any longer if you mount the fourth mounting bracket. Can also be an advantage if you cannot accidentally switch your Mac off.