A hydraulic bearing is a type of plain bearing used in fans, which are part of, for example, complete water cooling sets. Its principle involves utilizing a thin layer of oil between moving parts, which significantly reduces friction and wear. Unlike simpler plain bearings, it has a closed system with its own lubricant reservoir. This design prevents oil leakage and dust ingress, thereby ensuring constant lubrication. The result is quieter fan operation and a longer lifespan compared to basic bearing types.