Multiconductor cables contain two or more conductors. Each conductor consists of a single wire or a combination of wires. Conductor materials include aluminum, copper, aluminum alloys, copper alloys, aluminum-clad steel, and copper-clad steel. Aluminum has a density that is about one-third that of copper or steel; however, copper is the most widely used conductor material in wires and cables. Cable shielding is placed around an insulated conductor or group of conductors to prevent electrostatic or electromagnetic interference between the enclosed wires and external fields. Common shielding methods include braiding, drain wire, thin foil, and braided foil. Typically, the wires in stranded conductors are braided together. By contrast, paired cables consist of pairs of insulated wires that are twisted together. Stranding makes wires more flexible. Pairing increases the rejection of noise and interference.