This is the Futaba GY401 Gyro with an S9254 Digital Servo.
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.
Included high-speed S9254 digital servo boasts 47 oz-in torque and a
speed of .06 seconds @ 60°
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.
One year warranty

INCLUDES: One GY401 gyro
One S9254 digital servo, available separately FUTM0224
One 0.81" (20.5mm) round servo horn, one 1.8" (45mm) round servo horn
one 1.25" (32mm) 6 point servo horn, one 1.5" (39mm) 4 point horn,
mounting hardware
One mini plastic adjustment screwdriver
Three mounting pads
One instruction sheet

SPECS:    GY401 Gyro-                     S9254 Digital Servo
Length: 1.1"  (27mm)            1.6"  (40mm)
Width:  1.1"  (27mm)            0.79" (20mm)
Height: 0.79" (20mm)            1.4"  (36.2mm) not including horn
Weight: 0.95oz (27g)            1.8oz (50g)
Torque: 47 oz-in
Speed: .06 sec @60°

COMMENTS: Can be used in helicopters and airplanes (Due to 0-100% Gain Adjust).
The new SMM (Silicone 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 JR digital servos. These have a different pulse.
Voltage- use only with a 4.8V battery. (if you use it with a higher voltage battery it needs to be regulated to 6.0V)

Servo included is setup for large helicopters, such as the Trex 600 - not meant for Micro/Mini helicopters.