[.045 .065 .080 .100 .130] ProSteels Round Wound XLPROSTEELS The XLProSteel series is the most magnetic and brightest sounding electric bass string of all D'Addario strings. By using a special alloy, we have achieved a ``piano tone'' that is ideal for players who use steel strings, with rich overtones and a brilliant sound with an excellent balance between high and low frequencies. ProSteel is a completely new sound for steel strings.