Can be placed on treads after a True Kin installs the Motorized Treads cybernetics. Currently the only thing that can be placed on treads. The player gets two tread slots and will need to place guards on both to get the full +2 AV.
Can be tinkered with a couple of low-level bits and a 3 (BA3). Cannot be made wooly or spring-loaded, so you might as well mod them to be scaled and feathered for a massive +500 rep with Birds and Unshelled Reptiles.