We have a 2nd year 12U team and have used the TCB balls for a year now. What I've noticed with these balls is that they quickly separate out the kids with good mechanics from the kids that don't - the kids with good mechanics learn quickly how to make solid contact and drive the ball, and it has really benefitted them during games. The kids with poor mechanics may "learn" to hit these balls squarely, but it does not translate to driving the ball. These are the kids that need to spend extra time with a hitting coach on the tee fixing their mechanics, or they won't be successful - at best they are inconsistent hitters that spend a lot of time hitting weak pop-ups to the infield and not line drives. Don't be fooled for a minute that these balls will help any kid become a good hitter. It makes good hitters better, but the poor ones don't really benefit unless you can identify their flaws and work to fix them.