Gear transmission refers to a device that transmits motion and power between gears. Working through tooth-to-tooth anastomosis is a commonly used in modern equipment. A mechanical transmission. Cultivate children's interest in learning and desire for knowledge, enhance children's innovative awareness and ability, and strengthen the cultivation of hands-on ability. Power Suplly:2 x AA Battery(Not included batteries) Colour:As Shown Material:Wood+Plastic+Metal+Electronic Accessories Size:Finished product size:85x75x100mm Package Contents: 1 set * DIY Electric Gear Drive Model Kit (This is just a DIY kit, not a finished product; 2 x AA Battery is not included) Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.