This Koyo IR Series inner ring serves as an inner roller raceway in applications where the shaft cannot be used as a raceway, and is used with Koyo HJ Type heavy duty needle roller bearings. It is made of hardened and ground steel, and meets ASTM International standard ASTM F2431. The inner ring has an oil hole for lubrication in place. This Koyo inner ring is an accessory for use with Koyo HJ Type heavy duty needle roller bearings, which are used in various applications, such as automotive and truck transmissions, agricultural and construction equipment, pumps and compressors, and two-cycle engines, among others.

Roller bearings use rolling elements to maintain a separation between moving parts to reduce rotational friction and support radial and axial loads. These elements can be one of the following types: ball, cylindrical, spherical, barrel, needle, spindle, or tapered. Roller bearings can be open on both ends (a shaft can pass through) or open on one end and closed on the other. An open end can be sealed or shielded to protect the bearing from solid contaminants and moisture that could reduce its lifespan. If an end is sealed, the sealing component is an elastomer lip that contacts the shaft. If it is shielded, the shielding is a non-contact lip, usually made of metal. Rolling bearings are used in a range of applications from agricultural machinery to conveying equipment, robotics, dental equipment, elevators, rolling mills, ship rudder shafts, and aggregate crushers, among others.

Koyo Bearings USA manufactures needle roller bearings, bearing assemblies, and needle rollers for automotive and industrial applications. The company, founded in 2009, is headquartered in Canton, OH, and meets International Organization for Standardization (ISO) standards 14001 and TS 16949 for quality assurance.