Remember these colorful plastic clackers from when we were kids? It is basically a handle with 2 plastic balls attached on swinging arms. Rotate the toy just right with the correct speed and momentum and you can get them slapping and clapping against each other. It is fun when you can get the one arm to swing into a still ball, which then stops that one and puts the other in motion. Makes a cool repetitive sound for auditory learners. Makes a great party favor. Each clacker is 4″ tall and has a 3.5″ arm with ball.