Rare Phosphor Bronze. Acoustic Guitar Strings, handcrafted, stainless steel. RPML-11 (11-50) Acoustic Guitar Strings in Phosphor Bronze. Low tension... the sound is loud and warm. The Rare Phosphor Bronze strings offer a different approach compared to the standard, quality copper strings available. They are not necessarily better, but they possess a new, different, and more powerful "voice". When DR started producing a string with new characteristics, the goal was to redesign contemporary thinking about what phosphor bronze can offer to a good acoustic guitar. Handmade arch-tops and dreadnoughts, as well as fine acoustic guitars made from rosewood, maple, and cedar, seem to benefit from a noticeable improvement in sound, depth, and resonance with Rare Phosphor strings. Players seeking a fuller, more powerful sound, as well as deeper bass (those who enjoy hearing their guitars resonate), will appreciate the sound, tone, and feel of Rare Phosphor. According to our friend, who plays bluegrass extensively and is a three-time national champion on the guitar, Steve Kaufman, the Rare strings last unusually long. Steve recommends DR to all his students.