Single ball and double ball features: Single ball consists of one ball + one copper bearing. It is usually installed on the leaf surface and frame surface of the cooling fan. The balls will fit on the leaf shaft. Because the two kinds of balls have different materials, in order to achieve the same core degree, this production process will consume more work time. The main thing is that this is not the same as the core, which will cause its bearing friction sound to be abnormally large. After half a year of use, the friction sound will become more and more obvious. The micro-fan, the smaller the fan, the harder it is for a single ball structure. Therefore, it is generally not recommended to use a single ball structure for fans smaller than 7 cm.