D'Addario XSAPB1353 XS Hybrid Light Coated Phosphor Bronze A/G Strings, 13-53

The XS coating gives the warm, balanced phosphor bronze strings maximum life, with an uncommonly smooth feel. Made with a NY Steel core, phosphor bronze wrap wire and Fusion Twist technology, XS coated acoustic guitar strings have incomparable break strength and tuning stability, in addition to their dramatically increased lifespan.

eBay