Thomastik-Infeld Violin strings Infeld hybrid core - A Hydronalium (IR02)Infeld "Red" The strings of the red and blue set can be combinated to change the soundcharacter without changing the string tension. The red series amplifies the dark sound of the instrument, the blue string maintains the brilliant sound. With E string chrome steel, gilded Composite Core = Hybrid core 4 4 Size E Steel, gold plated, tension 8. 0kg 17. 6lbs A Hydonalium (alloy of aluminum, magnesium, manganese) wound, tension 5. 5kg 12. 1lbs D