In order for a ball or roller bearing to perform satisfactorily, the fit between the inner ring and shaft must be suitable for the application. For example, too loose a fit could result in a corrosion fretting and up to bearing race spinning on shaft. While too tight a fit could create a reduction in internal bearing clearance. The proper fits can only be obtained from tolerance standards set forth by ABMA & ISO standards organizations. The selection of the proper fit is dependent on the direction of load, bearing dimensions, operating temperature, heat expansion of shaft and other parts, material & wall thickness and required running accuracy.