Engineering plastic sliding bearings are produced from one or more types of high-performance engineering plastic that have been impregnated with solid lubricant and special reinforcing fibers through via polymer modification technology, yielding a self-lubricating plastic material. Sliding friction occurs in the gap between engineering plastic sliding bearings and their mating shafts, and not the rolling friction that occurs in plastic rolling bearings. Plastic sliding bearings are in face-to-face contact with their mating shafts, and lack the point contact that exists between the balls of rolling bearings and the bearings' inner and outer rings. This ensures that the load-bearing capacity of engineering plastic sliding bearings is greater than that of plastic rolling bearings, and the linear velocity of sliding bearings is typically lower than the linear velocity of rolling bearings. Because they are made from self-lubricating, wear resistant materials providing permanent solid lubrication, engineering plastic sliding bearings have a much longer service life than sliding bearings with ordinary surface lubrication. This is one reason why a growing number of engineers at manufacturing firms are choosing to use plastic plain bearings.