Designed to provide your fine guitar with enhanced protection. Martin Marquis Silked Phosphor Bronze strings have an added soft silk wrap on the ball ends preventing wear and tear on the bridge. The silk wrap adds a layer or protection enhancing corrosion resistance and providing reliable tuning stability. Manufactured with copper tin and phosphorous Phosphor Bronze strings yield a dark and slightly warmer tone that 80/20 strings. These Acoustic SP strings include gauge 12-16-25-32-42-54. Features Set of 6 acoustic guitar strings Light gauge 12-54 Metal wrap wire composition of copper tin and phosphorous Soft silk wrap added to ball ends Thread wrapping for enhanced corrosion resistance Specifications Gauges: 12-16-25-32-42-54 Tension: 168.5