Kids use solar power to get this water pump working…or use a standard battery when the sun isn’t shining! The kit invites children to build a dual-powered water pump. They just follow the step-by-step instructions to fit all the pieces in place…then add water to watch the pump come to life—for tons of STEAM fun exploring spatial reasoning and logic! Kit includes over 25 pieces, plus a guide—just use your own screwdriver! Pump base measures approximately 5 1/2". Requires 1 “AAA” battery (not included).