Excellent educational science gadget. Not only stimulate people's interest and exploration in physics, but also shows the laws of conservation of momentum and energy. Made of high quality metal and plastic, it is safe and smooth to touch. Great for home ornament, study or office desk table decor accessories, etc. A nice gift for friends, kids, family. sleek desk toy for adults and children! Requires 4pcs AA batteries to operate(battery not included), push it by hands and it will use the battery power to keep on swinging until the battery runs out. Specification: Material: Plastic, Metal Size: base diameter-10cm/3.9inch, height-30cm/11.8inch Package Includes: 1 Set Perpetual Motion Toy (Batteries are not included) Note: Please allow 1-3mm measuring deviation due to manual measurement. Due to the different monitor and light effect,the actual color of the item might be slightly different from the color showed on the pictures.Thank you!