This is the Savox SB-2231SG "Ultra Fast" Tall Brushless Steel Gear Digital Servo. 

Features: 

• Combines leading edge technology with super high 12 bit (4096) resolution and unique steel gears
• Ideal for use in Giant airplanes
• Brushless motor provides longer life and cooler operating temps
• Extremely strong unique steel gears ensure long-life and durability
• The full aluminum case design not only looks good but also allows for cooler and smoother operating temps
• Our servos are totally green – from materials to production, these servos are environmentally friendly
• Ideal for giant scale aircraft, monster truck, 1/8 scale

Specifications: 
Dimensions(mm): 40.3x20.2x45.0 
Weight(g): 84.0 
Speed(@6.0V sec/60): .14 
Torque(@6.0V oz-in): 444.4 
Speed(@7.4V sec/60): .10 
Torque(@7.4V oz-in): 555.5  40KG
Gear: Unique Steel 
Bearing: 2BB 
Case: Full Aluminum 
Spline: 25 Tooth