Roller bearings utilize either cylindrical, needle, tapered or spherical rollers. Rollers carry load on a line contact and as a result can support large radial loads. Cylindrical roller bearings consist of an inner race, an outer race, and cylindrical rolling elements. A cage allows the bearing to operate at high speeds. Long, thin rolling elements, called needles are well suited for bearings with a small diameter, or where high speeds are desired. Tapered bearings are ideal for combined loads. A tapered roller bearing is comprised of one or two cones and a cup. The cone contains an inner race, cage and tapered rollers which roll on the tapered surface of the cup. Spherical bearings are comprised of a concave outer raceway, convex rollers, and either a tapered or cylindrical bore. Spherical rollers enable high radial loads due to the large contact area between the rollers and raceways. In addition, the concave shape of the raceway allows the bearing to self align. Thrust roller bearings are intended for large magnitude axial loads with very little radial loading. They can contain either cylindrical, spherical, tapered or needle rollers. Applications for roller bearings include machine tool spindles, steel mills, and vibrating equipment.