Penn Championship High Altitude tennis balls set the standard for high performance on the court. A controlled fiber release provides the consistency players deserve and expect. Enjoy reduced shock after every swing thanks to the natural rubber construction. Interlocked wool fibers offer longer wear for extended use. For quality play every time you take the court, choose Penn Championship High Altitude tennis balls. Ideal for altitude above 3,000 feet USA League Tennis Official Ball Extra-duty felt recommended for hard courts, asphalt, outdoor or concrete surfaces Each can contains 3 tennis balls Important Note: These tennis balls are designed for use in high altitude locations over 3,000 feet. They will not work as well and seem dead or flat in other locations.