This component is a separate cylindrical inner ring designed for use with needle roller bearings that require a matched inner ring for the shaft seat. It has a bore diameter of 50.0 mm, a width of 25.0 mm, and a net mass of 78.26 g. The cylindrical bore allows direct mounting on a plain shaft without additional adapter sleeves. As a standalone ring, IR50X55X25-XL provides the running surface for the rolling elements and is selected together with a matching outer bearing unit rather than used on its own. Fitting a dedicated inner ring reduces wear on the shaft itself and allows the raceway to be replaced independently if it becomes worn, keeping the shaft usable.