There is no real visible difference between the two. Just small changes for strength in the upper rear bulkheads rear camber bridge steel diff gears, diff cases and the number on the box. I have the original kit and it works for me. Key tips, clutch build, gear alignment and mesh, and some type of brace. By the way I am trying to find a 4 mm chassis and all I see is the high traction chassis from mugen which I have, the Arena which is 3.3 and cso which is 3.2. Anyone tried these other chassis? I'm not completely satisfied with the high traction chassis even though it's better than the original.