xinyujie 8015 cooling fan MOQ:200pcs Payment:T/T,L/C, ... at 120 degrees centigrade. 4.The bearing type:we choose ball bearing. Ball bearing is a rolling friction from metal ... small, the friction coefficient is small; but sleeve bearing is sliding friction ,contact surface is big ,after ... long-term use, the oil would evaporate, bearing wear and tear, friction coefficient is big, noise ...