Royal Classics SN10B Sonata Nylon Guitar String Basspak, Medium-High Tension Extend the life of your favorite string set with Royal Classics custom Basspaks. Sonata basses deliver elegant, voluminous tone with a comfortable string resistance. The custom wound, medium-high tension Sonata Basspak is gauged .78mm/.031", .86mm/.034", 1.09mm/.043" and includes an extra #4 string. Treated with an ultra thin proprietary anti-oxidant coating. Crafted in Spain by and for serious guitarists.