Ball bearings with a plastic sheath are best suited for comfortable rolling and smooth running. This protects the running rail or other system components. There are many different materials to choose from, such as POM, PET, PA or TPE. All these submit distinctive properties in order to specifically address the respective customer requirements. As well, an optimally coordinated geometry of the contact surfaces significantly influences the lifetime and the abrasive wear of the roller and prevents flattenings of the plastic. For small series and/or high loads, the plastic sheath is made of semi-material, whereas granules are utilized for cost-optimized large series. Moreover, the steel parts of the sheathed ball bearings can be individually designed. In order to realize particular mounting conditions and to fulfill customer requirements.