This is the Hitec HS40 economy Nano servo.
Features:
Ideal for micro airplane, sailplane, and helicopters
Slightly larger than the Hitec HS-35HD servo
High impact nylon gears
Coreless motor
Long life potentiometer
Includes: HS40 Servo with 0.67 (17mm) 4-point horn, 2.2 (55mm) Double Arm Horn, 1.2 (31mm) Double Arm Horn, 1.1 (28mm) Double Arm Horn extra Servo Horn Screw, Two 1.5x7mm Mounting Screws
Specs:
4.8V
Speed: 0.09 sec/60°
Output Torque: 0.6kg/cm (8.4oz/in)
Weight: 4.8g (0.17oz)
Size: 0.79x0.34x0.67 (20x8.6x17mm)