States have devised separate free-wheel caster parts that make all the wheels moving in all areas. This system has a tank to run faster and respond to every surface.
America was invented Wheel separated from the suspension. That makes all the wheels are moving in all areas. Tanks with this system Make run faster And respond to any surface.
America invented the wheel. The independent separates from the bumper. For every wheel that moves in all areas. The tank with this system, run faster, and responding to all surfaces.