The TNP wall ball is great quality and maintains a round shape when used. It is ideal for wall balls and I do recommend. I chose the 10kg. My one and only concern is the weight distribution within the ball, it feels like the weight moves depending on which side you drop it. This sometimes makes it awkward when catching the ball as the centre of mass is not in the centre of the ball. This is possibly sand moving inside, which I expect will get better with more use as it distributes itself within the ball.