This is the Savox SH-1290MG Super Speed Metal Gear Digital Servo.

Features:

4096 super high resolution
Water-Resistant with 4 silicone seals
Coreless motor brings output performance to new levels - smoother, faster and more efficient operation.
The metal case design not only looks awesome but also allows for cooler and smoother operating temps.
Our servos are totally green – from materials to production, these servos are environmentally friendly.
Ideal as a rudder servo on 500, 600, and 700 class helis.

Dimensions(mm): 40.3x20.2x37.2
Weight(g): 56.4
Speed(@4.8V sec/60): .06
Torque(@4.8V oz-in): 55.5
Speed(@6.0V sec/60): .05
Torque(@6.0V oz-in): 69.4
Gear: Metal
Bearing: 2BB
Case: Aluminum
25 Tooth Spline