V18, brought to you in 2 very small diameters, offers a syntheses of perfect Touch, Speed and Spin. We additionally increased durability and reduced tension loss.   Material Core: Monofile Polyester Co-Polyester   Technologies Double Heating: this technology refers to a thermal after treatment consisting of a second heating process that is applied to the string. On the one hand, the double heating evens out any irregularities; on the other hand, it eliminates internal stresses. The result is pliable, uniformly elastic strings. Pre-stretched: Isospeed strings are pre-stretched. Pre-stretching the string core or the entire string reduces the loss of tension to a minimum. At the same time, this allows for lower tension weights. Liquid Wax: Once manufacture is complete the string is refined with a layer of wax. This layer simplifies stringing the racquet and significantly extends the life of the string itself by reducing wear.