This is the GY611 Gyro with SMM Technology from Futaba.
This is a High Performance, Compact and Light Weight
(AVCS) Angular Vector Control System gyro has a substantially improved tail control capacity and developed for model helicopters. Because the sensor and control circuit are integrated, it is simple to install.

Features:

AVCS System: Since the rudder trim changes (caused by wind and other
meteorological changes); the front, rear, and other heli attitudes
change and are automatically canceled; tail (rudder) operation is
easy, making it perfect for 3D flight.
(also known as heading hold gyro)
SMM Gyro Sensor: Use of this newly developed technology virtually
eliminates rudder trim changes during flight (see COMMENTS).
Digital Servo Compatible (DS Mode): DS mode makes it compatible with
Futaba digital servos. This maximizes the high-speed response
performance of the digital servo.
Remote Gain Function and Mode Switching Function Remote: Gain
function allows sensitivity switching from the transmitter and mode
switching function allows AVCS/normal gyro mode switching.
Integrated, compact and lightweight design made possible by high
density mounting technology.
Conductive Resin Case: This case improves EMC (Electrostatic and
electromagnetic interference) resistance.

Includes:

GY611 control amp ( x 1)

Sensor tape ( x 3 )

GY611 sensor ( x 1 )

Mini screwdriver ( x 1 )

S9256/BLS251 servo ( x 1)

GY611 Ratings

Yaw-axis stabilizer for helicopter (rate gyro)

Display device: 8-character dot matrix liquid crystal display

Operating voltage range: DC 3.8V to 6.0V

Current drain: 70mA (@5.0V, including sensor)

Dimensions: 57 x 32 x 15mm (amp), 30 x 30 x 18mm (sensor)

Weight: 34g (amp) + 30g (sensor)

S9256 Ratings

Dimensions: 40 x 20 x 36.6mm

Weight: 57g

Speed: 0.06sec/60ﾟ(at 4.8V)

Torque: 3.4kg·cm (at 4.8V)

* Special servo for the GY611/GY601

BLS251 Ratings

Dimensions: 40 x 20 x 36.8mm

Weight: 61g

Speed: 0.06sec/60ﾟ(at 4.8V)

Torque: 3.8kg·cm (at 4.8V)

* Special servo for the GY611/GY601