D'addario j53 muta ukulele hawaiian D'Addario J53 sets are designed for use with Hawaiian Concert ukuleles. Each string within this set is made from our warmest sounding black nylon. The original ukulele offering from D’Addario, each black nylon string is carefully center-less ground to an ultra-smooth, ultra-precise final diameter for excellent feel and unparalleled intonation with a warm, long lasting acoustic tone.  Black precision rectified nylon ensuring that the roundness and dimension control of each string are unsurpassed Preferred for their warm and long lasting tone String Gauges: Black Nylon .026, .032, .036, .028