Essentially, they are a large sphere with cutting and ripping tools attached to four legs, capable of latching onto, and eventually destroying, land vehicles. While almost insanely quick, easily able to outrun a military truck at full speed, they have little in the way of armour and easily succumb to any kind of opposition that has proper anti-armour weapons, added with the fact that only thin skin is sanctioned to protect its delicate machinery. This is compensated by their lethality against infantry (a drone can kill any infantry with just one jump) and their primary function - latching onto a vehicle and tearing it apart.