This Layer Fan holder is for 3 - 30MM X 10MM BLOWER FAN. These are the same ones that come with the Rostock Max. The Shape is the same as the Tricklaser Max Metal Platform. I have seen good results with this mount so far. The air doesn't feel to be blowing on the hotend. The height is quite tall, I had to put my standoff on the lathe and trim them down a bit.

Attribution - Creative Commons