This is an optional Traxxas X-Maxx/XRT Waterproof Digital High-Torque Servo.
The Maxx®-Duty metal-gear steering servo features full all-metal gears and ball bearings for increased precision. The Maxx-duty servo puts out 23% more torque than the standard 2085 servo to take on the most extreme environments. The kit includes a stiffer servo saver spring and steel steering linkage for maximum steering authority and control during high speed driving. Servo requires Maxx® mount found in Maxx, X-Maxx®, and XRT™. Does not fit other vehicles.