I'm very pleased with this puzzle.  First each train car is 98% complete on each piece.  It leaves just a small part of the animal(s) "missing" which helps the child locate the next piece (for example, part of the 5th seal is missing on the #5 train car -- my nephew looked for the seal's face in order to find the #6 car as he doesn't yet recognize the numerals.  The pieces are thick and will last a long time.  The pictures are attractive without being too busy although the pics on the higher numbers are not placed for easy counting.