Thomastik Infeld Red Composite Core 4/4 Violin Strings Medium IR100 From the creators of Dominant strings comes a breakthrough. Thomastik Infeld strings are relatively insensitive to humidity changes, break in quickly, and have relatively low tension. A new, synthetic composite core gives these strings a full sound and a longer life span than other synthetic strings, and are reponsive to different playing techniques. Red strings have a darker tonal quality and Blue has a brighter tonality. Removeable ball on E string.