A broad range of industrial applications require the movement of large, heavy objects. Aerospace is one such category, in which large airframes or engine parts are moved throughout manufacturing plants. Casters in these plants are high capacity, with load limits of several tons each or more. The caster wheels must be robust, and are normally forged steel, nylon, or metal with a polyurethane tread. In some cases they may be pneumatic or solid rubber, and the casters may be multi-wheel.