1.30 mm / 16 gauge. ALU Power is the top string on tour for a reason - the aluminum present in the string enhances playability to go along with impressive power and control. Its unique poly-ether-ether composition exceeds all quality standards for near-zero string variance. Completely impervious to atmospheric conditions such as moisture, ALU Power delivers unrivaled consistent performance for championship-worthy results. Wilson Luxilon ALU Power 16 Tennis String Set | Christy Sports