Von York ® Cryogenic series Acoustic Guitar Phosphor Bronze Strings Kelvinite® Acoustic Guitar Phosphor Bronze Strings Lights Dimensional stability means stable pitch with relatively little stretching, so they stay in tune longer. Phosphor Bronze – 92% copper and 8% tin with phosphorous. Bright and resonant, these strings are ideal for any situation. Musicians favor these strings for live performances and because they are Kelvinite strong,  you know you can depend on them. The world is yours with Kelvinite by your side.