Phosphor strings have a darker, fuller tone than 80/20 strings and add a bit of warmth. They have a tone that contains more mid-range and sound a bit fuller and rounder. Add that to Elixir's string coating technology which adds life to your strings and you get unequalled tone and string-life! Excellent choice for Grand Auditorium, Concert, and Parlor-sized instruments. providing enhanced articulation and clarity.