This is the Savox SB-2231SG Ultra Fast Brushless Tall Size 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.

    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
    Gear: Unique Steel
    Bearing: 2BB
    Case: Full Aluminum
    25 Tooth Spline
    Frequency: 250-333
    Pulse Rate Frequency: 1520