iPong Training

I bought 100 of these iPong training balls along with my iPong topspin robot. Havent tried the robot yet. IMO, I find about 50% of the 100 balls have that uneven line at the half dome. No 2 star label on the ball itself like advertised but its pretty hard when I press my thumb on it (feels like 2 star) Paid $20 for 100 balls.