Great long-lasting balls for clay court tennis
I've played with Penn Championship balls for many years and was always dissatisfied with how long they retained pressure. Figured it was normal for tennis balls, though. In the last 2 years, I went to Penn Tour Extra Duty for hard courts and Pro Penn Marathon Regular Duty for clay. Both kinds of balls last at least twice as long as Penn Championship balls in terms in terms of retained pressure. So they are definitely worth the extra cost of the basic Penn Championship ball.