differential on cyber10b

[what the f....]

So i open up the diff on my cyber10b (i didnt build it) and there is no oil or grease just gears like these,http://www.hpiracing.com/products/en/61433/, and there arnt any balls(On the hpi website it says that it comes with a ball diff) so what does a ball diff look like or is the diff i have a ball diff; and should i put oil or grease on the gears.