"Cooling Fan Manufacturer" means the air-cooled radiator fan discharge air per minute or included total volume, if calculated by cubic feet, the unit is the CFM; If you press cubic meter to count, is the CMM. Radiator air volume units are often used CFM (approximately 0.028 cubic meters / minute) 50x50x10mm CPU fan will generally reach 10 CFM, 60x60x25mm "Cooling Fan Manufacturer" usually reach 20-30 CFM. Air volume and pressure are two opposing concepts. In general, to design the 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 (which is why some high fan speed, air flow is large, but the cooling effect is bad reasons). Instead, the wind pressure, air volume is small, "Cooling Fan Manufacturer" not enough cold air subjected to heat exchange with the heat sink, the cooling effect will be poor.