This is a stress relieving bouncy ball fidget toy to help release nervous energy.
You print the two halves in TPU, thinly apply contact cement to the two flat sides, let the contact cement dry and then press the two halves together. Contact cement when applied in this manner is very strong and the ball will stay together no matter how hard you throw it at a wall or other object. You can also use it to strengthen hand grip by squishing it.
Kids love playing with these balls also.