They have a 25cc engine built into the right boot, including a dangerously hot exhaust and a plastic gas tank. They can propel you at up to 20 mph, but they don't have brakes. There is an emergency stop, but if you use it the boots stop instantly.
They're made in China, and illegal almost everywhere, and you can probably already find them on the Black Market.
Not to worry, though. The manufacturer has prepared a short instructional video:
The Counter of Doom!
