This is the Traxxas 2055 High-Torque Servo.  This has 80 oz/in of torque, making it an excellent steering servo.  This works well in the Traxxas T-Maxx, E-Maxx, Revo or any other vehicle that you would like to mount this in.  This part goes between the receiver and hooks to the steering or engine to provide the steering or throttle control.

This servo pair has been tested and confirmed to operate well.  See attached video.