D'Addario EJ67 Nickel Mandolin Strings, Medium, 11-39 D'Addario EJ67 mandolin strings are great for electric or acoustic mandolin playing. EJ67 mandolin strings are wound with nickelplated steel, known for it's distinctive bright tone and excellent intonation. String Gauges: Plain Steel .011/.011, 014/.014, Nickel Wound .025/.025, .039/.039