The RobotiKits from OWI have no comparison. For flawless assembly: 5 stars. For clarity of instructions: 5 stars. For durability of constructed robots: 5 stars. For robots that actually work as advertised: 5 stars. Let's face it - not all kits turn out as well as they are supposed to, but you can count on these kits going together and functioning with the perfection of precision engineered components. All kits come with a pre-assembled circuit board. Most components are made from plastic and either snap together, or hold in place with the provided screws. Some kits may require some additional tools listed below. What sort of knowledge will be gleaned while enjoying these fun kits? Gear structure, battery wiring, motor principles, electronic circuits, circuit block diagrams, and comprehending assembly instructions. Try one today! CHOKING HAZARD (1). Not <3yrs.