Luxilon Big Banger ALU Power 16 Gauge - 125 Polyester (Poly) Tennis String Set - 40 Feet - Silver THE STRING THAT PUT POLY ON THE MAP: Luxilon Big BAnger ALU Power 16 Gauge - 125 Polyester (Poly) Tennis String Set - 40 Feet in Silver is the string that helped usher in the polyester revolution. Its firm, monofilament construction allows for much greater durability, while helping players impart heavy spin on the ball. This string is designed for advanced players. STRING COMPOSITION: Unlike your average poly, Luxilon combined a co-polymer or nylon with a fluorocarbon resin and aluminum fibers. The result is a durable string that offers well-above average feel for poly, and really helps those revolutions per second most advanced players are after.