Santa Cruz Parabolic Tension Acoustic Guitar Strings Low Tension Santa Cruz Strings are engineered to do what others cannot, to put the exact tension on each individual string to create the appropriate download pressure. Santa Cruz Strings require precise core to wrap ratios and precision fit and finish for unprecedented tolerances of one half of one thousandths of an inch. State of the art metallurgy and micro-coating assures long life by preventing corrosive moisture from contacting the core of these nickel and lead free strings.