Xt strings feature an extended lifespan treatment on every string in the set, preserving the natural tone and feel of uncoated strings; High carbon steel wire and fusion twist technologies deliver unrivalled tuning stability and break resistance. Strings stay in tune 131 percent better than traditional strings; Strings last at least 4 times longer than traditional uncoated strings; The inner packaging features a re-sealable zip closure, for ease of opening as well as storage of unused strings; Every set includes a players circle code for product identification, registration, and authentication. Players can collect points to get rewarded with daddario products and merchandise; Country of Origin: United States