Very heavy duty. 1/8 scale diffs with optional lockers. Steel spur gear and tranny gears. Heavy duty links. And shocks. Beefy solid axles. Here is a couple pics of mine.
Attachment 922177
Attachment 922179
And for $150 you could own this roller with complete extra axle 4 diffs 2 lockers and 2 one gallon ziplock bags full of spares.