The softest premium multifilament string from Yonex is the Rexis Comfort 16/1.30 String Set. Thanks to the FRF (Fusion of Resin Filament) manufacturing method, it contributes to power generation while retaining excellent durability. Because Fortimo, a novel flexible substance, fills the spaces between the filaments, the string feels substantial and has more elasticity. WTA player Naomi Osaka uses Yonex Rexis in her racquet crossovers to give herself a little more strength.