The extruder fan is by far the loudest fan on an Anycubic Kossel (and probably many other cheap printers). So I wanted to use a more silent one, like the Noctua in the pictures. This is btw. the PWM version, because it spins at 5000 rpm instead of 4500 rpm like the FLX model, resulting in slightly more air throughput, still less than the original fan, though.
And here comes my Thing: It conducts the air through the cooling fins, without it the air is mostly pushed around and exhausted unused.
No supports or raft/brim needed, but do be careful when releasing it off of your bed, it is pretty delicate.
Be careful, when using Cura 3.6/4.0: It makes a notch of a quarter circle in the cylindric part, 1mm high and I don't know why, but Slic3r works fine, so you'd probably better use Slic3r for this one!
Be careful when removing this from your bed, it is rather delicate.