UltraSonic nickel bass strings are precision wound from premium grade, specially selected alloy materials. The formula unique to this string delivers a classic sound with warmer tone, excellent sustain, and longer life. The harmonic content of the strings provides a smooth, round top and wonderful low-end growl, making them particularly well-suited for fretless bass. The special core-to-winding ratio ensures each UltraSonic string set is properly tensioned for perfect balance and feel. Warm tone, low end growl, and the choice of pro bassists worldwide!