Balls to Square Mystery (spons)

Two sponge balls are shown. The magician puts one in his pocket, and the other in a spectators hand. With a magical gesture, the ball in the magician’s pocket disappears, and ends up in the surprised spectator’s hand, that now has two balls.
The same effect is repeated for three times, in different ways.
To end the routine, the magician puts three sponge balls in the spectator’s hand, and instantly they transform into a sponge cube!

• The balls have a diameter of about 4.5 cm and the cube measures 5.7 cm per side.