This is the Savox SC-1251MG Low Profile High Speed Metal Gear Digital Servo.

Features:

Super high 4096 resolution and metal gears.
Super light-weight.
Coreless Motor provides high speed, incredible efficiency, and low power consumption than comparable servos.
The aluminum case design not only looks good but also helps operation to remain cool and smooth.
Our servos are totally green – from materials to production, these servos are environmentally friendly.
Ideal as a steering servo for 1/10 surface applications and in gliders and airplanes that have thin wing profiles.

Dimensions(mm): 40.8X20.2X25.4
Weight(g): 44.5
Speed(@4.8V sec/60): .10
Torque(@4.8V oz-in): 97.2
Speed(@6.0V sec/60): .09
Torque(@6.0V oz-in): 125.0
Gear: Metal
Bearing: 2BB
Case: Aluminum
25 Tooth Spline