Each inverted Y-shaped pylon of the Millau Viaduct is equipped with 11 pairs of stay cables. Inside the protective sheaths, the strands are made up of seven twisted steel wires and put under a predefined tension. Depending on the length and tension of each one of the stay cables, 45 to 91 strands are required. Each strand has also been specially given triple corrosion protection through galvanization, petroleum wax coating, and an extruded polyethylene sheath. The outer casing of the stays is equipped over its entire length with a double-helical bead.