The ubrace mod is done in conjunction with the CHub. From my experience, it helps the car rotate is little better on a higher bite surfaces. I have found on low bite surfaces that it is pretty awful. Because the rear will slid a little and square up better, it adds a little more steering on the entry of the turn and when power is applied, it will square up nicely. Again, this is mainly for higher bite tracks. IMO if your running double Dee's you probably want the A hub. If your running a Bar code, beam or suburb type of tire, the C hub and ubrace mod might be for you. Like Matt said, the avid carbon upper is nice because it is an all in one A/C hub and is cheaper than the AE C Hub.