Nano-Carbon Shield AOT Coated Phosphor Bronze Acoustic StringsBlackSmith acoustic guitar strings are made with the finest materials and manufactured using state-of-the-art automatic servo controlled winding equipment. USA made phosphor bronze and steel ensures a long lasting string with increased sustain and purer & warmer tone.Our proprietary computer controlled winding technology produces strings with a very consistent wrap surface and even tension, resulting in stable tuning, accurate intonation, and superior playability.The Nano Carbon Shield AOT (anti oxidation technology) coating prevents oxidation and dirt build-up on the wound strings without altering the tone – a BlackSmith exclusive!! Sub-Zero treated plain steel strings offer brilliant tone with a silky feel. With BlackSmith Nano Carbon Shield coated acoustic guitar strings, you will experience the perfect balance of consistency, tone, and playability. Vacuum Sealed in Patented Anti Kink Packaging Prevents Oxidation and String Damage.