The HS-635BB utilizes the revolutionary Karbonite gear train. Karbonite is four times stronger than our standard nylon gears and even after hundreds of thousands of cycles it does not show any signs of wear. With a powerful motor, and dual ball-bearing mounted output shaft, the HS-635BB offers plenty of torque and speed. If your application requires increased speed and torque, the HS-635BB is the perfect upgrade from a standard size servo.