Because "Small Cooling Fan" bearing into two ball bearings and oil bearings, ball bearing AC fan long life, low noise, but the price is very expensive requirements. Oil-bearing ball bearing service life is shorter than 1/3, may be some noise (over one year) in use for some time, but cheap "Small Cooling Fan" price. After more understanding since we can choose, but if any ball fan fan oil prices and the price is almost the case, indicating that the ball bearings or the elimination of the old product, do not buy. And push for the manufacturers of the new "Small Cooling Fan" in the bearings (except clear that the oil-bearing outer) will not exceed the life of the ball bearing, and there will be noise in the future use.