J96 Cuatro-Puerto Rico Strings: D'Addario J96 strings are designed for the 10-string setup of the Puerto Rican cuatro, generally tuned in fourths, B to E. These strings deliver a warm, full-bodied tone perfect for the celebrated national instrument of Puerto Rico. The wound strings are of silver-plated copper wound onto a silk and steel core. The unwound strings are tin-coated steel for a distinct festive sound.