Spherical plain bearings have an inner ring with a sphered convex outside diameter and an outer ring with a correspondingly sphered but concave inside surface. Their design makes them particularly suitable where alignment movements between shaft and housing have to be accommodated, or where oscillating or recurrent tilting or slewing movements must be possible at relatively slow sliding speeds. Spherical plain bearings require regular relubrication as the sliding contact surface combination is steel-on-steel. The high wear resistance of the sliding surfaces makes these bearings especially suitable where heavy loads of alternating direction, shock loads or heavy static loads have to be accommodated.