Mini Air Cooling Fan styles

"Mini Air Cooling Fan" similar on the market vary, which play their own skills to buy, here come about, which parameters need to refer to when buying
1, the pressure value.
2, "Mini Air Cooling Fan" fan size.
3, to determine the fan is DC or AC.
4, balls or oil-bearing in the form of fan.
5, the fan supply voltage value, for example: AC 220V, 110V, 380V DC 5V, 12V, 24V, 36V, 48V.
6, "Mini Air Cooling Fan" speed, for example, wind turbines, how many cubic meters, or how many cubic feet per minute per minute.