Whether you're a seasoned veteran trying to perfect your game or a rookie learning the basics, Penn tennis balls are the number one choice. The best- selling tennis ball in America, Penn Championship is the standard by which all other tennis balls are measured. It features a controlled fiber release for perfectly even nap, natural rubber for consistent feel and reduced shock, and interlocked wool fiber for ultimate durability. The Extra Duty felt is designed to perform best on hard courts, but can be effectively played in any setting. The Official Ball of USTA Leagues, the Championship line provides unparalleled consistency every time you hit the court. Available in several bulk case sizes up to 24 cans with 72 tennis balls total.