Penn Championship Extra Duty (XD) Tennis Balls (10 Cans/3 Balls Per Can 30 Total Balls) 10 cans of 3 balls for a total of 30 balls Extra-duty felt is ideal for hard court play Natural rubber offers a consistent feel and reduced shock Interlocked wool fiber for longer wear; deep elastic seams prevent cracking USTA/ITF approved for competitive play; official ball of USTA League Tennis