The needle roller bearing is the roller bearing with the cylindrical roller. Relative to its diameter, the roller is thin and long, so this roller is called the needle. Despite the smaller cross-section, the bearing still has a higher load bearing capacity, especially suitable for the occasions with limited radial space. Depending on different occasions, we can select the bearing without the inner ring or the needle and the cage to assemble the bearing, and take the bearing journal surface matched with the bearing and the porous surface of the shell as the inner and outer rolling surfaces of the bearing. In order to ensure that the load capacity and operation performance are the same as those of the bearing with a ring, the surface hardness, the machining accuracy and the surface quality of the shaft or shell porous roll should be similar to those of the raceway of the bearing ring. Such bearing can only bear radial load.