This is the Futaba GY401 Gyro and S9254 Digital Tail Servo combo.  This is a high performance, compact and lightweight Angular Vector Control System (AVCS) gyro developed for model helicopters.  Because the sensor and control circuit are integrated, it is simple to install.  The included high-speed S9254 Digital Servo boasts 47 oz-in torque and a blistering speed of .06 sec/60°.

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.  The included high-speed S9254 Digital Servo boasts 47 oz-in torque and a speed of .06 sec/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
One  .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

Specifications:
GY401 Gyro:
Length: 1.1"  (27mm)
Width:  1.1"  (27mm)
Height: .79"  (20mm)
Weight: .95oz (27g)

S9254 Digital Servo:
Length: 1.6"   (40mm)
Width:   .79"   (20mm)
Height:   1.4" (36.2mm) not including horn
Weight: 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 (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 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 6V).