BASS STRING SET 4-string bass set for XL series Nickel Round Wound, (050-067-090-120). The D'Addario Balanced Tension XL Bass Guitar Kits are made up of mathematically optimized string gauge combinations, resulting in more control and comfort performance. Combined with the distinctive bright tone of the XL Nickel Wound strings, each set offers greater dynamic control and a more consistent feel between strings for strumming, balanced bendings, picking and other techniques.