Intermediate and advanced tennis players looking to add more power and spin to their game should try the Solinco Confidential 18 1.15 tennis strings. These co-polyester strings are designed to generate intense spin and maximum power while also increasing feel and control on the court. An innovative chemical composition combines with a high-powered polyester monofilament to amplify power and bite while also improving tension maintenance. With the Solinco Confidential 18 1.5 tennis strings. you'll increase spin with every swing.