Thomastik Infeld Super Flexible Rope Core Violin Strings Medium 4/4 Thomastik-Infeld Superflexible violin string's solid core has been replaced by a cable-type structure made up of braided steel threads. This reduces stiffness, and improves elasticity. A Superflexible string is extremely responsive and its tone seems to literally radiate from the instrument, without being harsh. Durability, tuning stability, and open fifth purity are extraordinary. Superflexible is a dependable all-round string for the discerning musician, at home with every type of bowing and in every musical situation.