Material: high-grade plastic and iron<br />Principle: outside force caused the swinging and then use a battery (9V square integrated battery) into the energy continues to swing until the battery is discharged<br /><br />Package list:<br />Celestial sphere * 1<br />Stand * 1<br /><img src="http://img6.eachbuyer.com/x9/p100/eb02161_1.jpg" />                                                        <img src="http://img6.eachbuyer.com/x9/p100/eb02161_2.jpg" />                                                        <img src="http://img6.eachbuyer.com/x9/p100/eb02161_3.jpg" />                                                        <img src="http://img6.eachbuyer.com/x9/p100/eb02161_4.jpg" />                                                        <img src="http://img6.eachbuyer.com/x9/p100/eb02161_5.jpg" />