The hub bearing is a critical rotating support component situated between the vehicle wheel and the axle; it bears the vehicle's weight, ensures smooth wheel rotation, and provides wheel speed signals to the ABS (Anti-lock Braking System). Characterized by an integrated double-row structure, first-generation hub bearings come pre-lubricated and with preset axial clearance from the factory, requiring no maintenance after installation; they represent the most widely used product type in the aftermarket. Based on rolling element type and structural design, first-generation hub bearings are categorized into three main series: DAC double-row angular contact ball hub bearings, DU double-row tapered roller hub bearings, and TB paired single-row tapered roller bearings. Each type offers distinct advantages regarding load-bearing capacity, friction characteristics, maintenance requirements, and application suitability, collectively meeting the needs of vehicles ranging from micro-passenger cars to heavy-duty commercial vehicles.