This is the GY401 Gyro with SMM Technology from Futaba.
This is a High Performance, Compact and Light Weight
(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 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: 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

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 the JR digital servos. These have a different
pulse.