This type of bearing is suitable for components with particularly limited radial dimensions. Due to the absence of a ring, the surface of the shaft neck and the inner hole surface of the shell serve as rolling surfaces, and the hardness, surface roughness, and dimensional accuracy of the inner hole surface of the shell that matches the shaft neck surface should be comparable to the bearing ring. There is also a type of pivot cylinder that is changed to a flat headed cylinder and adopts an "M" - shaped cage structure, which greatly improves the speed performance.