In and Out Box (mini) $6.50

A small red box (1.5 ” tall) is opened to find a black box inside. When the black box is opened it is found to be empty. You then start over. putting the red box together and placing inside of the black box.  But how is that possible? Which is the smaller box? When the black box is once again opened and the red box is opened a sponge ball is found inside the red box.