XT STRINGS FEATURE AN ADVANCED CORROSION RESISTANCE 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 UNRIVALED TUNING STABILITY AND BREAK RESISTANCE. STRINGS STAY IN TUNE 131% BETTER THAN TRADITIONAL STRINGS!. HIGH CARBON STEEL WIRE AND FUSION TWIST TECHNOLOGIES DELIVER UNRIVALED TUNING STABILITY AND BREAK RESISTANCE. STRINGS STAY IN TUNE 131% BETTER THAN TRADITIONAL 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 D’ADDARIO PRODUCTS AND MERCHANDISE .