The Instinct Response provides max stability, durability and high energy return. The material used is Ultranyl and it is a revolutionary material able to fix all the weaknesses of traditional nylon (tension maintenance, durability) and enhance its positive features (power, feel and comfort). Instinct Response is a blend of Nylon 6 and Nylon 6.6 which, combined in a secret co-extrusion formula, determine a new standard in the nylon strings world. The string is made in Italy by DoubleAR.