Martin's M600 ukulele strings are clear fluorocarbon and suitable for soprano or concert models. The use of modern fluorocarbon increases the amplitude and improves the harmonic output. The increased tensile strength holds tunings longer. String Gauges: .0191, .0256, .0340, .0216Set: M-600Gauge: Soprano/ConcertTension: 30Get everything you need for your ukulele right here and remember, accessories ship fast from Sam Ash Direct