The biggest fault with these toys is that they're on the lighter side of Ben Wa Balls. If you're a beginner or looking to give someone a present, I recommend you take a look at these balls. They're high quality with a great storage pouch and classy packaging all for a fairly low price. If you're a more experienced user, you might want to find a heavier set of balls.
The most helpful critical review
The most expensive marbles I've ever owned.
The price of these means they aren't too intimidating of a purchase, even if they're not perfect for you. If you think you need somewhere easy to start with Kegels, these might be a good place. However, I think most women would do better with something heavier.