This would be a costumer service question, but I will answer the best I can.

The box will depend on what all is inside, but usually the smaller boxes are used for smaller items, which is close in size to the larger pop tart boxes, just a little bigger. If there are more items or that is the only size box they have, you will get a larger box, which is about as tall as a cereal box, but wider on the side wall. And the front wall is about half the size of a cereal box.