GraviTrax POWER: Switch & TriggerShift the direction of your marble run automatically with the "GraviTrax POWER Element Switch and Trigger" and take the path to exceptional fun! Control your marble's path like never before handsfree! As a marble passes through, the POWER Trigger signals the POWER Switch via radio (RF) waves to shift the direction the next marble takes along your track! Power up the possibilities and build even more complex marble runs! Makes an excellent addition to