This is the Hitec HS-985MG Coreless Ultra-Torque Heavy-Duty Universal Servo.  Because this has the universal connector, it will work with JR, Hitec, Futaba, and Airtronics Z radio systems.  These are great for up to 1/4 scale airplanes, helicopters, and steering and throttle for 1/10 and 1/8 on- and off-road cars and trucks.

FEATURES:
Dual ball bearings
Water and dust resistant
Coreless motor
Three metal gears and one Karbonite gear
MOSFET motor drive
Indirect drive potentiometer
Gold plated contacts

INCLUDES:
Hitec HS-985MG Coreless Ultra Torque Servo with 1.8" (45mm) diameter horn, 2.3" (59mm) double sided arm, 2.8" (72mm) double sided arm, 1.5" (39.5mm) single sided arm, mounting hardware and info sheet

REQUIRES:
Installing in model and connecting to receiver

SPECS:
Operating Speed: 0.16 sec/60° at 4.8V
0.13 sec/60° at 6V
Output Torque: 133.31 oz-in (9.6 kg-cm) at 4.8V
Weight: 2.18oz (62g)
Size: 1.57 x 0.78 x 1.45" (40 x 20 x 37mm)

COMMENTS:
A note on coreless motors: conventional servo motors have a steel core armature wrapped with wire that spins inside the magnets. In a coreless design, the armature uses a thin wire mesh that forms a cup that spins around the outside of the magnet eliminating the heavy steel core. This design results in smoother operation and faster response time.