2WD Smart Robot Car Speed Detection Chassis Kits With 20 Grid Encoder For Arduino Feature: Simple structure， easy to install 3mm acrylic material 1:48 strong magnet gear motor Diameter 78mm wheel 20 grid encoder， using with speed module to make speed detection system 6 x AA battery holder， convenience to power With switch， easy for ON \/ OFF Using EMC motor， not disturb SCM Can be used with Arduino main-board， L298N driver module， 3 channel tracing module to form smart robot car system Package included: 1 x Acrylic glass 2 x Wheels 2 x Fitments 1 x Switch 1 x Omni-directional wheel 2 x Encoders 2 x Motors 4 x Copper pillar