Wilson US Open Regular Duty tennis balls set the gold standard for the best players in the world. These premium tennis balls provide the consistency you deserve, with a premium woven felt for ideal performance on clay or indoor courts. It's easy to see why they've been the top choice at the US Open for over 40 years. When the game is on the line, put your trust in the Wilson US Open Regular Duty tennis balls. ITF and USTA Approved Official ball of the US Open Made with premium woven felt. Provides ideal performance on clay and indoor courts Comes with an eco-friendly overcap that cuts the amount of plastic used in half. The overcap helps prevent balls from spilling out even when turned upside down.