This toy consists of two hard plastic balls, usually made of acrylic or a similar material, held together by a string.

Players hold the strings, and by moving their hands up and down, they can make the balls swing and collide, producing a clacking sound.

The object of the game is to make the ball swing in rhythm and "clack" together, creating a satisfying sound.

It takes some skill and practice to get the technique and rhythm right.