Ernie Ball strings are carefully crafted using the highest quality materials to ensure superior tone and reliability. The specially tempered high carbon steel core wire's hexagonal shape ensures the wrap wire is securely held in place through the length of the string. Precision crafted Swiss brass ball ends are attached with a triple lock twist. Made of specially tempered tin plated high carbon steel. This string is great for use on electric and acoustic guitars, banjos and mandolins but, not classical guitars.