This is the GY401 Gyro with SMM Technology from Futaba.
            This is a High Performance, Compact and Lightweight
  (AVCS) Angular Vector Control System gyro 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 cancelled; 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: One GY401 gyro
          One mini plastic adjustment screwdriver
          Three mounting pads
          One instruction sheet

SPECS:    GY401 Gyro-
            Length: 27mm
            Width:  27mm
            Height: 20mm
            Weight: 27g
          Voltage- use only with a 4.8V battery. (if you use it with a
            higher voltage battery it needs to be regulated to 6V)

COMMENTS: Can be used in helicopters and airplanes (Due to 0-100% Gain Adjust).
          The new SMM (Silicon Micro Machine) technology is the integration
            of mechanical elements, sensors, actuators and electronics all
            brought together on a common substrate chip. This hobby industry
            first, results in a gyro sensor with an unprecedented level of
            functionality, reliability, and sophistication.
          This will not work with the JR Digital Servos. These have a different
            pulse.