When D"Addario introduced the world to phosphor bronze strings in 1974, guitarists everywhere fell in love with their rich and warm tone, and string manufacturers everywhere quickly jumped on the band wagon. But D"Addario phosphor bronze strings, like EJ15s are different. They"re kind of like a good pair of designer jeans — they start off feeling comfortable and broken in (not stiff or rigid) and yet they seem to last forever!