"Micro Cooling Fan" only three blades is not surprising, the most common fans is the case, but in the small DC brushless fan this design is rare. As mentioned above, an excessive number of blades, too close, will increase air turbulence and blade surface friction, reduce fan efficiency, increased operating noise. Designed for some of the heat sink without too much pressure with this 4cm trefoil "Micro Cooling Fan". Reducing the number of leaves, leaf area in order to increase the inclination also will be reduced, so a certain level of pressure has weakened. Although the lack of pressure, but the larger the distance between the blades, the fan efficiency, to ensure maximum air flow can still be at the same time, working pressure reducing noise. Personal recommendation: the "Micro Cooling Fan" design pressure is low for smooth passage design environment uses less cooling requirements.