Needle roller bearings are a kind of roller bearings equipped with thin and long rollers, which are called needle rollers. The inner sleeve of a needle roller bearing, also known as the inner ring, is one of the key components of a needle roller bearing, which is located in the interior of the bearing and is in direct contact with the needle rollers, playing a role in supporting and guiding the needle rollers. Steel sleeve, on the other hand, usually refers to the steel shell or sleeve used to protect or support other parts, in needle roller bearings, steel sleeve may refer to the inner sleeve or jacket (outer ring) of the material of steel parts.

Needle roller bearing inner sleeve is widely used in various mechanical equipments such as automobiles, machine tools, metallurgical machinery, textile machinery and printing machinery, etc., especially in the occasions that need to withstand large radial load and the radial mounting size is restricted.