The string choice for Roger Federer, Champion's Choice Duo combines the power and feel of Wilson's Natural Gut with the durability and spin of Luxilon's ALU Power Rough. 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. Hybrid of Wilson Natural Gut and Luxilon ALU Power Rough Roger Federer's string of choice Ideal blend of power, spin, and feel Hybrid set comes with two types of string Natural Gut (16g / 1.30mm) Luxilon ALU Power Rough (16L / 1.25mm)