BOJIN Newton's Cradle Balance Ball Science Puzzle Desk Toy - Mirror - Medium We have showed 4 types of ball collision as a reference. It has more types of impact combination.Players can enjoy the creativity and experience the fun of physics. Please do not pull-up to a too high degree ,45will be proper. Because the higher the position of the swing ball be pull-up, the greater the impact force to the stationary balls ,and it may lead to tangle up. It is suggested that do not let your little kids play with this unsupervised . Medium : 5.3 x 4.5 x 5.3 inches Large : 7.1 x 4.7 x 7.1 inches When you received the item,please take the balls out one by one to prevent the balls tangled up. It is suggested be placing horizontally.