This specification covers round and grooved hard-drawn copper- and silver-bearing copper trolley wires. Copper materials shall be of such quality and purity that the finished product shall have the properties and characteristics prescribed herein. All wires shall conform to the following physical properties: tensile strength, elongation, dimensions, density, and electrical resistivity. Three twist tests shall be made on round wires between the holders of the testing machine for the purpose of determining developing defects that may be prejudicial to the life of the trolley wire. Wires that do not withstand at least nine twists without breaking shall not be considered satisfactory. The twist test shall be omitted for grooved wires. All wires shall be of uniform size, shape, and quality throughout, and shall be free from all scale, flaws, splits, and scratches not consistent with the best commercial practice.