I am a preschool teacher and bought this for the classroom. They kids love it. The colors add inventiveness to the configurations. The pieces are easy enough to fit together but don't fall apart whenever you breathe. We have used it with regular sized marbles and sand. The kids love to see how to put the tubes together and make mazes to find out where the sand or marbles will fall out. They also construct imaginative "castles" and "houses" from them. My only complaint is that I didn't buy 2 or 3 sets while they were on such a great sale! One child could get by with 1 set, but with more children and creative minds, other sets would have been well-used.
(Review on Amazon)