Casters are rolling mechanisms used to support and maneuver mobile items such as carts, racks, dollies, and other material handling equipment. Casters and wheels are often confused. Wheels are one component of a caster. Casters refer to the whole caster apparatus, including the framework, attachment unit, and the caster wheel. Some casters may be referred to as heavy-duty casters, depending upon their caster load capacity, wheel diameter, and tread width. Heavy-duty casters support heavy loads, and can transport material across a variety of surfaces in extreme applications. Industrial casters can be heavy-duty casters or light-duty casters, depending on the application. Industrial casters commonly include specific caster wheels with materials such as forged steel, cast iron, and polyolefin, used to transport material across a variety of surfaces in specific environments. Some casters have dual wheels, designed for large capacities and distribution of floor load. Swivel casters are a type of caster that has the ability to swivel, allowing for a 360-degree shift in direction and ease of maneuvering. Swivel casters can have a wheel brake with a foot-operated lever connected to its axel, to compress the caster frame against the center of the caster to prevent rolling. Swivel casters may also have locks to hold the casters in a stationary position. Casters are often selected for their specific caster mounting system, which is typically a plate, stem, or ball attachment mechanism. Casters are used in a variety of industries that require casters, including health care, manufacturing, commercial, instructional, and food service.