Penn Championship Extra Duty Tennis Balls (Pack of 12 Cans) (36 Balls) This is a bundle of 12 cans of Penn XDuty Tennis Balls and 1 InPrimeTime Tennis Ball Car Magnet Ideal for Hardcourt play, but also suitable for Har-Tru and Clay Deep elastic seams for reduced cracking Interlocked wool fiber for longer wear. Natural rubber for consistent feel and reduced shock Comes with InPrimeTime Tennis Ball Magnet to Show Your Tennis Love (InPrimeTime Exclusive)!