In general, to design "Waterproof Cooling Fan" air volume, it is necessary to sacrifice some pressure. If the fan can bring a lot of air flow, but the pressure is small, the wind can not blow the bottom of the radiator. Conversely, a large wind pressure, air volume is small, there is not enough cold air subjected to heat exchange with the heat sink, the cooling effect will be poor. General aluminum fin heat sink requirements "Waterproof Cooling Fan" of pressure is large enough, and copper fin heat sink fan requires a sufficiently large amount of wind; dense fin heat sink fins relatively sparse compared to the heat sink, the need for greater pressure fan, otherwise poor air flow between the fins, the cooling effect will be greatly reduced. So different "Waterproof Cooling Fan", manufacturers will meet the appropriate amount of wind, air pressure of the fan as needed, rather than the pursuit of a single volume or high-pressure winds fan.