The motion subsystem includes 3 motors, 1 servo with 120 degree range of motion, and replacement gears for each. There are also 4 – 2.75″ tires, 2 – 4″ tires, 2 – 5″ tires, 2 intake rollers, and an assortment of 12, 36, and 60 tooth drive gears. The tires are plastic and hard rubber but appear sturdy. The gears, also plastic, seem less robust. Time will tell.