Needle roller bearings are roller bearings with cylindrical rollers. The rollers are as thin as needles, with a diameter generally not greater than 5mm and a length-to-diameter ratio greater than 2.5. This design makes needle roller bearings compact in radial structure and high in load bearing capacity, and they are particularly suitable for supporting structures with limited installation dimensions.

Needle roller bearings can be divided into various forms such as inner ringless bearings, needle roller and cage assemblies according to different use occasions. They can only bear radial loads and cannot bear axial forces. During installation, the hardness, machining accuracy and surface quality of the journal or housing hole surface must be ensured to ensure the operating performance of the bearing.