Available in 2", 2.5", 3" or 4" square tube helices thickness are available in 3/8 and 1/2 Helices material conforms to ASTM A36 hot rolled plate All helix leading edges sharpened and rock cut and 45 degrees. Corrosion protection to conform to ASTM A153 standard for hot dipped zinc coating Square Tube eliminated over torquing concerns associated with pipe style helicals Efficient torque transfer Clear visual indicator of torsional deflection