Penn Championship tennis balls represent the standard by which all other tennis balls are measured with consistent feel and playability every time you step onto the court. They feature a controlled fiber release for consistent nap, natural rubber for consistent feel and reduced shock, and interlocked wool fiber for longer wear. Penn Championship is the Official Ball of USTA Leagues. They are USTA and ITF approved (USTA National Campus, 2019) and is available in extra-duty felt, regular duty felt, or extra-duty high altitude felt. The Championship Line provides quality play every time you hit the court.