Use the aluminum pieces on the lower arms and the plastic upper B block. A good upgrade is the aluminum upper B block because the plastic one flexes to much. On the rear use the supplied aluminum pieces. A trick that I learned from the jammin guys is to drill and tap a hole for a set screw in the lower B block and the rear toe plate, also the upper B if you get the aluminum one, to hold the pin from turning and wearing the aluminum. This way only the arm wears and cheaper to replace.