Spherical plain bearings are used to accommodate shafts or rods with varying amounts of misalignment. They are designed to manage high radial loads and provide consistent performance under conditions of marginal lubrication, extreme speed and critical-application stress. Most spherical plain bearings consist of a plain bearing and ball bushing inside a lined, cylindrical housing that minimizes friction or provides self-lubrication. Lubrication-free spherical plain bearings are also available. Typically, metal balls and liners are made of steel, bronze or iron. Non-metallic balls and liners are usually made of plastic, nylon, or polytetrafluoroethylene (PTFE). Both metallic and non-metallic products provide superior performance to conventional steel, plastic or bronze plain bearings. For heavy-duty industrial applications, spherical plain bearings often include large bores or spherically shaped rollers that permit axial loading and relative misalignment between the housing and shaft.