These assemblies provide high accuracy and load carrying capacity with good rigidity and low radial sectional height. The running surfaces for needle roller and cage assemblies must be a suitable hardened and ground surface. Otherwise, a suitable inner ring must be used. The cages of this series are manufactured from steel, plastic for smaller diameters (TN) or brass for larger diameters. These assemblies are also available in double row (ZW) or split design (D). Please note that the items in .special sizes designation. column are not readily available and should not be used for new designs.