Review on 🔌 GeeekPi 2PCS Raspberry Pi 4 PWM Controllable Fan with Speed Adjustment - 40x40x10mm, DC 5V 4010 Quiet Fan for Raspberry Pi 4, 3 B+, Pi 3 (Black) by Tim Clark

First of all this is a bigger fan than I was planning to order. I was looking for a PWM fan to replace the "standard size" fan that comes with most cases. My fault is what it is. With that being said and not wanting to deal with returns I decided to go ahead and modify my case to use it and I'm very glad I did! This fan is configured as a "pull" fan. I personally prefer push fans on the Pi. To use it as an exhaust fan, it barely fits between the camera and displayport if you use one of the "9-layer cases". And the screws are uncomfortably long in my opinion, I would definitely shorten the screws so that they are slightly countersunk in the fan. You definitely won't be able to use it in a pull configuration in a case like mine with thermal clocks. On the plus side, this fan is VERY quiet, much better than 20mm fans, and the PWM control works as expected. 1 minute stress test, in forced configuration the fan was able to drop the temperature from 75°C to 62°C in about 15 seconds (where I had the fan shutdown on/off). May I recommend it? Of course, if you have a case for a 40mm fan or you don't mind modifying the case.