If 3-pin non-PWM fans are connected to this fan hub, this fan hub CANNOT give them extra PWM function. They will run at FULL SPEED.; If 4-pin PWM fans are connected to this fan hub, DUTY RATIO of all PWM fans can be adjusted at the same time. That is, all PWM fans will run at the same DUTY RATIO. Only speed of Fan 1 can be identified by the system; Capable of connecting to 4 PC fans simultaneously for cooling the computer system; When connecting multiple fans, be sure to connect the first red connector first; When connecting multiple fans, they must be fans of the same brand and specification; Support cable management