Everlasting tone for your acoustic guitar. DAddario XT Phosphor Bronze Custom Light Acoustic Strings will maximise the sonic performance of your instrument. Precision engineered their cores are made from high carbon NY steel and have special "Fusion" twist ball end fastenings enhancing tuning stability. And thats not just a vague claim - extensive testing shows that these strings will stay in tune 131 percent better than standard strings.Theyre long-lasting too. A new and improved microscopic coating process extends the life of the strings making them 42 percent stronger than other standard strings on the market. So this means you wont have to put up with the hassle of restringing your guitar all the time. These are strings that are designed to stay the distance - all the while giving your acoustic excellent tone.