BASS STRING SET 4 Strings Set for Electric Bass XL Series Semi-Flatwound Super Light (040 - 060 - 075 - 095) - Long Scale. D'Addario Half Round Bass Strings are covered with pure nickel, leaving the outer surface smooth and semi-flat, retaining the flexibility of round wound strings. Maintains the brilliance of the round wound and its sustain thanks to our exclusive "heat treatment" process.