Hi there,
my son wants one of these balls, from what I have seen from the neighbour's child's ones, they throw them on the floor and they open.
On the TV advert and on Amzon, Ebay etc I can only see the type that open when they are rolled on to a card.
So is the one you throw on the floor called something else? Or are my son and neighbour dping it wrong by throwing them on the floor? ( I did see one of them break after a hard throw) 
Thanks if anyone can enlighten me, they are apparently, very important for his happiness this Christmas!!