Royal Classics RC10B Professional Nylon Guitar String Basspak, High Tension Extend the life of your favorite string set with Royal Classics custom Basspaks. Professional high-hension basses deliver projection, volume and rich harmonics. The Professional Basspak is gauged .84mm/.033", .89mm/.035", 1.12mm/.044" and includes an extra #4 string. Treated with an ultra thin proprietary anti-oxidant coating. Crafted in Spain by and for serious guitarists.