Nylon or Steel Ukulele strings. Select above! Nylon String Gauges: 028, 041, 033, 028. Ideal for standard (re-entrant gCEA) tuning on Tenor, Concert and Soprano ukes. Also tune to aDF#B on a Soprano. Steel String Gauges: 033, 021, 014, 011. Suited for linear tuning (eg. DGBE) on steel strung Tenor and Baritone ukes Steel strings are Ball ended .