These strings build upon the materials and specifications of our Phosphor Bronze series. They include the addition of our LongEvo nano-technology treatment which creates an imperceptible microfilm shielding to provide exceptionally long life.These eco-friendly strings are completely free of chemicals, fully ecological and biocompatible to have no impact on the environment while maintaining unaltered tone characteristics, elastic properties and playability. Even after significant use our LongEvo strings retain their unique and exceptional voice.