Yonex PolyTour REV 17 / 1.20 Tennis String Bright OrangeYonex PolyTour REV 17 1. 20 Tennis String Bright Orange 1 Set Control and Spin Yonex co polyester monofilament helps you gain even more control into your game out on the court. Silicone Oil Infused Filament (SIF) technology reduces the friction between strings, resulting in faster ball speed and improved spin. For baseliners with medium to fast swing speeds looking for a shaped string (8 sided) that grabs onto the ball for the ultimate spin