RARE™ phosphor bronze bass strings are constructed upon a hex core. combining winding techniques developed by DR's long-lasting Lo-Riders™ and DR's rich, ringing RARE™ phosphor bronze acoustic guitar strings. RARE™ phosphor bronze acoustic strings are a departure from the standard bronze string currently available. possessing a new, different, and stronger "voice". When DR set out to produce a string with new characteristics, the goal was to redesign contemporary thinking