Wilson's new Spin Effect Hybrid Tennis String provides a great blend of spin, control and comfort. This hybrid combines a spin-friendly co-polyester string and a responsive multifilament that results in a great option for spin effect racquets. Construction: Co-polyester Monofilament / Multifilament Color: White/ Natural Gauge: 17G 1.25mm / 16G (1.30mm) Length: 21' / 20'