Expert strings. D'Addario XT NPS Medium Guitar Strings far exceed the norm when it comes to quality. Made with strong high carbon NY steel, they've been specially developed to excel in performance. They're up to 42% stronger than regular strings, and stay in tune 131% better. You can keep these beauties on your guitar for much longer - without having to worry about them breaking or going out of tune. They'll also give you the ultimate feel and tone - your riffs will sound sharper than ever before. Built with a new and improved microscopic coating process, they're the future of guitar strings.