Needle roller bearings are equipped with thin and long rollers (the length of the roller is 3~10 times the diameter and the diameter is generally not more than 5mm), so the radial structure is compact, and the inner diameter and load capacity are the same as other types of bearings. The smallest diameter, especially suitable for radial support size limited support structure. Needle roller bearings should be combined with bearing rings and applications depending on the application. A needle bearing is a bearing unit that combines a radial needle bearing and a thrust bearing component.