Phosphor Bronze Acoustic Guitar Strings wound on Hexagonal Cores. Normal tension, sweet tone, and bright treble. Our intention in developing Pre-Alloy phosphor bronze strings was to achieve for acoustic players a high quality, long-lasting string that is bright and unusually well-balanced in tone (first) and volume (second). This is an entirely All-American Alloy phosphor bronze strings of great clarity and great durability. Gauges: .013, .017, .026, .034, .045, .056