Now here is the kicker...I ran a ball diff when I first put the car together, running the GTB with a neo one 3 star (yes, they are compatible)..tore the ball diff out the frame in like 3 minutes. So, why the spool in the Hara kit if it sucks? And trust me, it does. The one way makes braking a chore. My Pro 2 was easier to drive, but it was a task with the cells. And, seeing that there are no CVD's made of steel, what is available (another manufacturer maybe) that has STEEL for the power of the 4.5? I treated myself to this vehicle and I feel that HPI is crapping on it favoring the cyclone. While the cars essentially are the same, why no support and hop ups for the Pro 4? HPI got me with the Pro 3 (I had one, carbon fibered out) and I hope they didnt get me again