2WD Smart Motor Robot Car Chassis Kit Speed Encoder Battery Box For Arduino 1:48 Brand new and high quality. Mechanical structure is simple, it is easy to install. This car is the tachometer encoder. With a 4 AA battery box. 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. Gear Motor reduction radio: 1:48. Size: 22cm x 14.7cm, wheel size: 7cm x 7cm x 2.6cm. Note: motor power supply is 3V~6V. All the parameter above is tested without load.