The second thing to consider in selecting an extension cord is wire gauge. Gauge is the thickness or diameter of the copper wires in the cord, and it affects how much current the wire can carry, along with how much the wire heats up. In the AWG rating system, the smaller the number, the thicker the wire. As an example, a 12-AWG, 120-volt cord contains 12-gauge wires and is intended for use with standard 120-volt outlets. An 18-AWG cord may only be rated for 5 to 7 amps of load at a length of up to 25 feet, but to get the same load rating with a 50-foot cord, the cord must have 16-AWG wire. Most extension cords made for light duty use 14- to 18-gauge wire. For medium, typical AWG ratings are 12 to 16, and for heavy duty, 10 to 14.