This is the Traxxas X-Maxx Waterproof Digital High-Torque Servo. This metal gear (ball bearing) waterproof servo also includes the servo saver spring and assembled steering link.
The X-Maxx steering servo includes full metal gears and adds a massive 23% more torque to take on the most extreme environments. The kit also includes a stiffer servo saver spring and steel steering linkage for increased precision and control during high speed driving.