DC geared motor mix standard 6 mm shaft at front commonly used in all robotics models available in 200 RPM (specific the RPM required) Center shaft geared motors specifically built for robotic applications provides a wide variety of options Easy to use and mount, standard size for all RPM, a huge variety of RPM available, long durability with distinct features These motors open a wide choice to fit with almost all wheels and chasis. Metal Gears inside thus low noise and high torque at shaft output.