Actionmaster Rumbler's exosuit - the blue wrecking ball attachments to the front wheels.
Originally they were softish plastic (they might have even been rubbery, but I can't remember), but mine and Demonac's have shattered upon touching them. They are too fragile to even pull out of the wheels.... and this is probably something all suffer from now, not just out-of-packaging ones (due to age of the softer plastic).

Not sure if I should just try to glue mine back together, or buy a new complete one and just never touch it ever.