Needle roller bearings are separable radial bearings with very low sectional heights that feature high load carrying capability. Needle roller bearings use long, slim rollers, the so - called “bearing needles” as rolling elements.
Due to the possibility of mounting inner and outer rings of needle roller bearings separately, mounting becomes much simpler, even under the conditions of mass production. The comparatively thin - walled needle roller bearing rings are usually mounted with tight fits.

In the case of bearing arrangements which work in very limited space, (e.g. gear boxes), needle roller bearings are frequently used without inner rings, designation (RNA). In these cases the bearing needles run directly on the shafts surface. These running surfaces, however, must to be designed to the same quality standard as for bearing rings, (e.g. hardened and ground).

Since needle roller bearings allow for length compensation of a certain amount within the bearing, they are optimum as non – locating bearings.
For applications where the non – locating bearings require large axial displacement, and it is not technically or economically feasible to harden and grind the shaft surface, needle roller outer and cage assemblies can be combined with separable wider inner rings.