The Wilson Nxt Duramax Tennis String features Xycro Micro-Fibers impregnated with Pu for enhanced comfort and power. The Nxt is the most popular multifilament string and features a larger sweet spot than traditional synthetic gut string and a fraction of its shock. For installation, handle gently and avoid over-clamping and crimping. This string is perfect for the players looking for a Nxt string but with added durability.