Jack's Guitarcheology is an official D'Addario dealer.

From D'Addario:

D'Addario was the first to use Phosphor Bronze in acoustic guitar strings back in 1974. Today, Phosphor Bronze is played throughout the world and considered to be the standard in acoustic strings, thanks to its beautiful sonic balance and tonal warmth. Our pioneering Phosphor Bronze acoustic guitar strings are precision wound with phosphor bronze wrap wire over a high-carbon steel core, providing tonal versatility suitable for all acoustic styles and musical genres. These 11-52 Custom Light gauge strings have slightly more volume and projection than Extra Light, while still being easy to play.

• D’Addario Phosphor Bronze acoustic guitar strings are precision wound with phosphor bronze wrap wire, over a hexagonal high-carbon steel core.
• Phosphor Bronze wrap wire provides tried-and-true D’Addario acoustic tone, with beautiful balance and warmth suitable for all musical genres.
• Now the standard in acoustic guitar strings, Phosphor Bronze strings were originally pioneered by D’Addario in the 1970s.
• D’Addario Phosphor Bronze acoustic guitar strings come with a code on the recyclable VCI bag, which you can register to earn Players Circle points.
• Our Phosphor Bronze strings are made in the USA—drawn to exacting specifications at our New York production facility