... we choose the fans ,not base on the speed, when the cooling efficiency are same, we choose ... demand,we choose the fans with lower speed, Cause lower speed,longer life span. 3.The material of ... material, RD signal (Stall warning), FG signal(Detect fan speed value), water proof and so on.4.CEETIFICATE:CE: ... . If you have any special needs for the fan specifications, please let us know. We will provide ...