The IR12X15X16-XL is a separate cylindrical inner ring intended to be pressed onto a shaft, providing a hardened raceway for needle roller and cage assemblies or drawn cup needle roller bearings supplied without their own inner ring. Bore diameter is 12.0 mm, width is 16.0 mm, and net mass is 7.8 g. Using a separate inner ring lets the rolling elements run on this hardened surface instead of directly on the shaft, so the shaft itself does not need to be hardened or ground to bearing tolerances, and the ring can be replaced independently if the raceway wears. The cylindrical bore mounts directly on a shaft of matching diameter and pairs with any needle roller bearing designed for a 12 mm shaft seat and this width.