This specification covers two sizes of extra-high-strength grade of concentric-lay steel wire strand, composed of seven, zinc-coated steel wires, specifically intended for use as the supporting messenger in Figure 8-type communication and electrical cables. Steel wires shall be manufactured by the open-hearth, basic-oxygen, or electric-furnace process. Materials shall adhere to specified mechanical and physical requirements such as breaking strength, elongation, ductility, nominal diameter, and coating weight and adherence. Zinc coatings shall be continuous and of reasonably uniform thickness, and wires shall be free from imperfections not consistent with good commercial practice.