Standard Size Range Round Type Enameled 0.50 mm Aluminum Wire is sometimes used in large transformers and motors, but due to its low conductivity, the cross-sectional area of aluminum enameled wire must be 1.6 times that of copper wire in order to obtain comparable DC resistance. Magnet wires with a smaller diameter usually have a circular cross-section. Thicker aluminum magnet wires are usually square or rectangular (with rounded corners) to allow more efficient use of the available winding space.