Flat cage assembliesare cages made from either plastic or metal and a large number of precisely guided rolling elements. Needle rollers provide a minimal construction height and optimum load carrying capacity and rigidity whilst cylindrical rollers are less demanding with regard to the connecting structure and have a slightly less rigidity. Balls create the lowest level of friction of all rolling bearings.Flat cage assemblies are designed for use with precision guideways but can also be used directly with customer-specific elements with appropriate raceways.