The string choice for Roger Federer, Champion's Choice Duo combines the power and feel of Wilson's Natural Gut (16/1.30) with the durability and spin of Luxilon's ALU Power Rough (17/1.25). Federer uses Natural Gut in the mains and ALU Power Rough in the crosses for a softer feel and superb playability. For better durability, use ALU Power Rough in the mains.