Wilson US Open Extra Duty tennis balls set a golden standard for the top players in the world. These premium tennis balls offer unrivaled consistency, making them the trusted choice at the US Open for over 40 years. A premium woven felt withstands extended use on hard courts. If you want to play like the pros, choose the Wilson US Open Extra Duty tennis balls! ITF and USTA Approved Official ball of the US Open Made with premium woven felt. Provides ideal performance on hard, abrasive courts.