BASS STRING SET 4-string bass set for XL series Nickel Round Wound, Long Scale, long scale (045-065-085-105). - D'Addario XL Nickel bass strings are world renowned as '' The Bassist's Choice '' whatever style you play. 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 excellent tuning for all styles.