BASS STRING SET 4-string bass set for XL series Nickel Wound, Regular light, Bright Round Wound, Double Ball, long scale (045-065-080-100). D'Addario XL Nickel bass strings are world renowned as '' The Bassist's Choice '' whatever style it plays. XL strings are wound with great precision with nickel plated steel onto a hexagonal shaped core, resulting in strings with a distinctive, brilliant tone and excellent intonation. Nickel plated steel wire wound to the core is known for its distinctive bright tone and fine tuning for all styles.