Needle roller bearing
（重定向自Needle roller）
A needle roller bearing is a bearing which uses small cylindrical rollers.The difference between a needle roller bearing and roller bearing is the ratio of diameter and length of their rollers, when the ratio of the diameter and the length of roller of a roller bearing is between the interval of 0.1 to 0.4, that roller bearing is called a needle roller bearing. They are used to reduce the friction of a rotating surface.