The Grand Prix Tennis Ball series is renowned for its excellent longevity and performance. These tennis balls perform well and feel wonderful to play with thanks to a unique rubber core technology and premium felt. On any court surface, the Dunlop Grand Prix Regular Duty tennis balls are ideal for competitive play. For major competitions like the WTA 500 Credit One Charleston Open and the WTA 1000 Miami Open, these tennis balls are the official selection. They contain a unique rubber core for a wonderful feel and a brilliant, high-end feel for improved visibility. The Grand Prix Regular Duty tennis balls are a great choice for serious and professional tennis players because Dunlop is the USPTA's approved ball brand.