Performer shows two balls, one red and one black. In full view of the audience, he pushes them into his fist. When he opens his hand, the red ball is seen to have grown to about four times its original size while the black one has multiplied into a number of smaller ones. A great visual change effect that is easy to do. Complete with instructions. Goshman quality.
Two sponge balls of equal size both change, one expanding and the other shrinking.