Eco-friendly Handmade Natural Bamboo Wooden 12 Digits Solar Power Calculator - with Solar panel (Model 1)-By VolksRose Full bamboo color, to switch off automatically without operation for 12 minutes. There are 18 keys in this bamboo calculator, using solar panel bamboo calculator and button batteries to supply the power. Handmade and crafted from responsibly sourced bamboo. Solar powered - No batteries required. Makes a great gift!