This is the HSR-5990TG Coreless Digital Robot Servo.

FEATURES: Durable titanium alloy gear with dual ball bearings
Programmable digital amplifier with MOSFET drive
Created specifically for the hobby robotics market
Motor Heatsink
Bottom Side Axial Mount Hole
Water and dust tight
Ultra Hardness shaft with 2 axial metal bushings
Overload protection

INCLUDES: One Hitec coreless digital HSR5990 titanium geared robot servo
One 1.03" (26.2mm) aluminum servo arm
One bottom case

SPECS:    Size: 1.57" x 0.78" x 1.45"  (40 x 20 x 37mm)
Weight: 2.39oz (68.00g)
Torque: 333.29 / 416.61 oz.in (6v/7.4v)
Speed: 0.17 / 0.14 sec @ 60 deg.
Operating voltage: 6.0 to 7.4V
Max speed: 0.17 sec/60 degrees at 6.0V
0.14 sec/60 degrees at 7.4V
Stall Torque: 24.0kg.cm (333.29oz.in) at 6.0V
30.0kg.cm (416.61oz.in) at 7.4V
Operating Angle: Max 180 degree
Connector wire length: 300mm (11.81in)