And Then There Were Four 2

A spectator hold an octogonal sponge in his hand. The magician touches his hand with a coin. When the spectator open his hand, there are two sponges.
The spectator close again his hand, and the magician touch again his hand with the coin. When he open his hand, the spectator discover now 3 sponges !
Finally the spectator close his hand for the last time and the magician ask him if he is waiting to see 4 sponges...He touches the hand with the coin and request the spectator to open his hand. There is an enormous 4 in his hand !
Easy to realize.