This is the motorized construction set that allows young engineers to build 25 working models. It consists of the classic shiny, metal girders, nuts, bolts and also includes a 6-volt motor, clutches, and ball bearings that turn wheels and propellers or lift mechanical arms. Children can build replicas of classic machines, including a crane that lifts objects, an airplane with spinning propellers, and a cherry picker truck with a bucket that moves up and down. The included hard-plastic case has individual compartments to keep parts organized. 638 parts. Requires four AA batteries. Ages 10 and up. Case: 16 1/2" W x 14" L x 4 1/4" H. (7 1/4 lbs.)