One of Yonex's most popular strings on the ATP tour and used by the likes of Nick Kyrgios and Frances Tiafoe, Poly Tour Pro provides great durability in a slightly soft.er poly. Made of a monofilament core but finished with high polymer polyester,this string really helps to put spin on your shots. Yonex pre-stretches this string under controlled temperatures for better durability and tension maintenance. The string feels very controlled and helps to reduce fatigue. Despite its slightly soft.er feel, Poly Tour Pro is definitely a low-powered string that will lend to players who take big swings at the ball or want a great hybrid poly option.