"Micro Cooling Fan" specific speed performance is a dimensionless parameter, so the fan according to equation (4-21) to calculate the ratio of the value of physical quantities related to the number of revolutions per unit, while the unit's speed n (rpm) and flow when units (Q3 / s) remain unchanged, the ratio of the number of revolutions ns only and full pressure p20 units concerned. Our fan model prepared in the ns value that p20 uses the results of the project's units, "Micro Cooling Fan" unit is kgf / m2 or mmH2o. When p20 using International System of Units, ns value has changed. Specific speed in engineering units larger than the use of SI units than 5.54 times the number of revolutions. "Micro Cooling Fan" ordinary fan, 73 more than the number of revolutions is to use the results of engineering units value calculated when using the International System of Units p20, specific speed becomes 13.21, according to the model designation of the fan should be 4-13 type fan.