Custom signature 4 string set for mandolin that is a personal set of Bill Monroe, an American mandolin player, singer and songwriter who created the style of music known as bluegrass. Strings deliver superior sound and long-lasting performance, and feature premium phosphor bronze winding over a hexagonal core of premium Swedish steel, for true tone and maximum response. Stings utilize strict quality control methods to ensure tone, durability and consistency. All Gibson strings feature specs absolutely unique to Gibson and are factory sealed to guarantee freshness in every set. Gauges: .011, .015, .026w, .041.