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.Sub-Zero treated plain steel strings offer brilliant tone with a silky feel. With BlackSmith 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.PB-1152 - BlackSmith original "hybrid gauge" Phosphor Bronze acoustic set, for players who want a warmer tone in a comfortable combination of gauges that offers the depth and projection of light gauge bottom strings, but slightly less tension on the plain strings for easy bending.