Casekingdom Smart Robot Car Chassis Kit Speed Encoder Battery Box For Arduino Smart car chassis tracing car Robot car chassis with code dis. Ideal for DIY Mechanical structure is simple, it is easy to instal. This car is the tachometer encoder With a 4 AA battery box (batteries not included) Can be used for distance measurement, velocity Can use with other devices to realize function of tracing, obstacle avoidance, distance testing, speed testing, wireless remote control