Wilson's Duo Power is a hybrid string that blends NXT Power with ALU Power for an explosive string bed second to none. For ideal playability, reduce tension on ALU Power at least 10%. Either string can be installed in the mains for superior power and performance. FEATURES: Blend of NXT Power & ALU Power Ultimate power Reduce tension on ALU Power at least 10% for ideal playability MATERIAL: Poly-Ether-Ether, PU COLOR: Silver Wilson Tennis String WRZ949710