Needle roller bearings are equipped with thin and long rollers (roller diameter D≤5mm, L/D≥2.5, L is the length of the roller), so the radial structure is compact, its inner diameter size and load capacity are the same as other types of bearings, and the outer diameter is small, especially suitable for radial installation size limited bearing results. Bearings without inner rings or needle roller and cage components can be selected according to different use occasions. At this time, journal surface and shell hole surface matching with bearings are directly used as inner and outer rolling surfaces of bearings. In order to ensure the same load capacity and running performance as bearing with rings, the hardness, machining accuracy and surface quality of shaft or shell hole raceway surface should be similar to the raceway of bearing rings. This bearing can bear radial load only.