Wilson Champion's Choice Duo is the hybrid tennis string set famously used by Roger Federer, combining Wilson Natural Gut for power and feel with Luxilon ALU Power Rough for durability, spin and control. Federer strings the natural gut in the mains and ALU Power Rough in the crosses for a soft, playable feel; reversing it (poly in the mains) adds durability. The set gives players the best of both natural gut and premium polyester in one package. • Hybrid: Wilson Natural Gut + Luxilon ALU Power Rough • Gauges: Natural Gut 16 (1.30mm), ALU Power Rough 16L (1.25mm) • Roger Federer's string of choice • Blend of power, spin, feel and durability