4 Pack 1.4 inch Ultra Soft Sponge Balls - Red by Ronjo

The basic sponge ball effect is beautifully simple:
A magician places one soft sponge ball in their own hand and another in the spectator’s hand. With a magical gesture, the ball in the magician’s hand vanishes. When the spectator opens their hand, they discover both balls have impossibly gathered together in their palm.
That’s the core effect objects appearing, disappearing, multiplying, and traveling, all happening right in the spectator’s closed hand, which is why sponge ball magic hits so hard.