American Educational Two Potato Clock, 8-1/2" Length x 3-1/2" Width x 2-3/4" HeightLED potato clock runs on 2 potatoes, oranges, grapefruits, lemons or cans of soda pop Designed to demonstrate the principle of an electrochemical cell Easy to Use Blue Plastic Potatoes not included The potato clock is designed to demonstrate the principle of an electrochemical cell. The LED clock runs on 2 potatoes, oranges, grapefruits, lemons or cans of soda pop. Potatoes are great mashed, roasted, baked or in clocks! Potatoes not included.