Rod end bearings are used when components must be joined together, such as a shaft or piston head. Two common variations of rod end bearings include solid and ball joint. Solid rod end bearings are one-piece, consisting of a through bore, a solid housing and shank. Ball joint rod ends are perhaps the most common and are available in either two or three pieces. Two-piece rod end bearings include a spherical bushing encased within a single-unit housing and shank. Three-piece rod end bearings are comprised of a single unit housing and shank, spherical bushing, as well as an inner race. The shank may have either male, female, or no threading. A shank with external threading is called male, while internal threading is called female. Materials of the housing, spherical bushing, and inner race vary depending upon the load, friction and rotational requirements. Materials include, steel, stainless steel, nylon and aluminum. Rod end bearings are commonly used in vehicles but are also utilized in machining centers, lift trucks, cranes, and fitness equipment.