Fully satisfactory fan
I bought this fan to put on the back of my case which has a fan slot but no fan supplied. I tested both directions (inward and outward airflow) and finally it is the outward airflow that best reduces the temperature at the motherboard (which was my problem in the first place).
The fan is quiet and its speed is automatically adapted by the motherboard (you have to set it in PWM mode in the BIOS).