This is the all new Scion xA / xB 600HP Level 3.9 Axle/Hub Kit. This set starts with a standard size spline going into the diff, made from high grade aircraft quality material. We then went on to make the center bars out of aerospace grade material and 25% larger and significantly more torsional, to absorb launch stress. The factory outer CV spline was just too small to handle increased horsepower, so we used our proprietary 26 spline outer from our other Level 3.9 axle kits. The kit also includes custom hub that is a replica of the factory hub, but with the larger spline to accomodate the larger outer CV. This is the only level axle set we will be making for the xA / xB, rated to 600HP with a 1-year warranty.