The quality control for the Penn Champs is not all that good either. It seems like most cans contain one substandard ball -- sometimes, a cosmetic reject but usually one ball has a substandard bounce.
Both the overall quality and and the quality control of the Prince Tours (and Prince Champs) are much better than the Penn Champs (altho' the Penn ATP balls are ok). The longevity of the Prince Tour appears to be 3x or better than the Penn Championship ball.
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I think you've had better experiences with Prince balls than many of us. Although I'm not personally familiar with any of the factories that make tennis balls, its been my experience that Prince balls can have too much glue which has a tendency to break off and you have a rattle after about ten minutes of play. I know of instances where all the balls in tournaments were taken out of play specifically for this reason - involved a huge number of cases. This situation has happened more than once and hopefully Prince has corrected the problem.
I cut several of the balls in half and the glue joints were like a paint can that had been used but on the inside - dripping down.
Its not a uniform drip which can make the ball a little off center also because of the weight of the glue.
Now, I've seen this with Penn balls also but the difference seems to be that the glue doesn't seem to harden and break off.
There can't be many places in the World that make tennis balls and I wonder if anyone know how many there are and does one factory make balls for several tennis companies?