Harmony Acoustic Guitar Strings are made in the USA with phosphor bronze precision wound onto a steel core, resulting in a string with long-lasting, balanced acoustic tone and excellent intonation. Favored by players for their bright and warm qualities, phosphor bronze wound strings are suitable for a wide variety of genres and playing styles. The strings come with an anti-corrosion inner bag for longevity and are available in five different gauges for all types of players, starting from standard gauges to custom gauges for different tensions depending on each player’s preference. The 12-53 gauge is great for players looking for a fuller and punchier tone. Thank you.