PROFORCE 521000 Premium Wheel Bearing and Hub Assembly (Rear) The new design is called roller-formed or orbital formed, which can effective avoid axial-direction moving of the hubs ring. The reliability of the hub is increased. Tighter control of assembled bearing clearance (no need to account for interference fit between inner ring and hub shaft). The flange is thicker, which will increase the rigidity of the hub and effective avoid the possible distortion of the flange when the vehicle turns or is hit by outside force. New design has 2 rolls of non-symmetric steel balls, i.e., outer side steel balls are larger than the inner side ones. Number of steel balls is also increased. This design ensures that both rolls of steel balls have the same lifespan and increase the overall lifespan of the hub. Overall, results in a more accurately operating bearing with a more controlled installed preload.