Work on your game all year long with the Penn(R) Championship High Altitude Tennis Balls 6-pack. The natural rubber composition reduces shock while offering a smooth feel for accuracy. Enjoy a game above sea level with the high altitude compression design of these balls. Deep elastic seams keep your newest set of tennis balls fresh by reducing cracking. Perfect your swing this year with the Penn(R) Championship High Altitude Tennis Balls. FEATURES: Multi-pack includes 6 cans (18 tennis balls) High altitude tennis balls for surfaces over 3,500 ft. elevation Natural Rubber composition for consistent feel and reduced shock Deep elastic seams for reduced cracking Model: 521419