It is made of strong neodymium iron boron (NdFeB). 216pcs 5mm diameter ball to be one set. Bucky balls are the perfect desk toy for anyone. Great for relieving stress, boredom and unleashing your imagination. Build and engineer limitless shapes and structures. Endless combinations. It is up to your patience and creativeness. This toy is not suitable for children under 14 years. If kids are under 14 years old, should be accompanied by adults when they play it. It will be a great gift for youth, teenage kids. Besides, it will also be a good toy for adult to less their stress. Suitable for office use, used for creativity and craft decoration on your desktop. You can put your logo on the lid. It is a good way to promote your company, business activities, products etc.