Made of high quality carbon steel, good toughness, high hardness, sturdy and durable, wear-resistant, accurate measurement. Heavy duty & good construction, a great tool for doing large carpentry work, scribe, drafting, drawing circles, metal work, and leather work. Lockable wing provide quickly measure, copy measurement, repeat measurement, measurement transfer and repeated circle drawing. The tips are hard and sharp, they can clearly & easily draw lines on the surface of metal, plastic, wood and other workpiece. The leg is 12.0 inches long, the maximum span (Radius) is 16.2 inches, and maximum drawing circle diameter 32.0 inches.