Stainless alloy originally engineered for extreme industrial conditions. Exceptionally corrosion-resistant with more flexibility than typical stainless steel. Perfect surface stays perfect for the life of the string. Available in Soft, Medium, and Hard.  Strings should generally be changed every 6–12 months, though students usually change them less frequently. Even if strings haven't broken, they gradually lose their brilliance and responsiveness — if your instrument sounds dull or takes longer to settle in tune, it's time for a fresh set.