Tubes are cylindrical components most commonly used in plumbing and other fluid transfer applications. They are usually made of metal or plastic and are made by extruding or drawing a material such as copper, brass, aluminum, polyethylene, or polyvinyl chloride. The most common type is a straight-length tube, which is cut to length and then generally bent, flared, or threaded to fit its application. Other tube varieties include helical coils, round tubes, and square or rectangular tubes. Depending on the material, tubes can be sectioned, swaged, flanged, bent, welded, and filled with a variety of components such as valves, fittings, and clamps.