"24V DC Cooling Fan" double ball bearings are more upscale, in the form of rolling friction, using two ball bearings, there are several pieces of tiny ball bearings around the axis, when the fan page or the axis of rotation, ball that followed rotation. Because all spheres, so friction is small, and there is no leakage problems. "24V DC Cooling Fan" is the advantage of dual ball bearing long life, about 50000-100000 hours; good anti-aging properties, suitable for high speed fan. "24V DC Cooling Fan" shortcomings double ball bearing is the high manufacturing cost, and maximum noise level at the same speed. "24V DC Cooling Fan" closed double ball bearings and hydraulic bearing wind better, especially the double ball bearings. Double ball bearing fan is embedded in the whole, there is no direct contact with the rotating part of the outside world. In a sealed environment, bearing more stable work environment. Therefore, the level of large-caliber 5000 rpm