This is the Savox SA-1230SG Monster Torque Steel Gear Digital Servo.
SAVSA1230SG Savox CORELESS DIGITAL SERVO 0.16/500 @6V

Features:

• Extremely strong unique steel gears ensure long-life and durability.
• Ideal for steering on rock crawlers, monster trucks, and large scale aircraft.
• Slightly taller case design.

Specifications:

• Torque @ 4.8v - 30.0kg/416.6oz-in
• Torque @ 6v - 36.0kg/499.9oz-in
• Speed @ 4.8v - 0.20 sec/60 deg
• Speed @ 6v - 0.16 sec/60 deg
• Dimensions L x W x H (mm): 40.3 x 20.2 x 44.9
• Weight: 79g