BASS STRING SET 4-string D-string for bass guitar Addario ProSteels Reg light Top / Med Bot, Super Bright Round Wound, long scale (045-065-085-105). The ProSteel Strings are our brightest and most magnetic strings. A special steel alloy offers us great harmonic richness and brilliance along with a depth of sound, this set of features work together to obtain the much sought-after piano tone. Perfect for both finger playing and plectrum playing. ProSteel strings will give you the punch you need in the mix.