This Yonex Poly Tour Air is the perfect strings for people with a softer, more controlled on-court style. It is a co-polyester string with a monofilament core that is finished with a high polymer polyester combined with HR Elastomer. Plushy “HR-Elastomer” built into the string helps to reduce shock onto the arm and returns to shape after bending to keep a consistent feel. This is stretched under a controlled temperature condition that results in greater durability, reduced fatigue, and fresh clean contact. With 200 meters of sky blue string, you will be set for a while.