I use this to keep the ptfe coupler cooler than normal and make it last longer. I used a 30x30x10 24v fan connected to the extra 24v output of the umo+ board and connected to this pwm external https://www.youmagine.com/designs/pwm-external-case to be able to turn it off or on manually. Ideally it should be a 25x25x10 and 5v fan, but they are more expensive. I can heat perfectly to 248-253C without any problem. But it takes more time if you put some fans to it. I should adjust the PID, but since it just works and the temperature remains stable I don't bother.I really recommed to drill the two m3 holes where the long screws go in, with a 3mm drill so it passes without friction (not the x4 fan holes).