This is a GY611 and BLS251 gyro and servo combo set for helicopter use.

GY611 Gyro
The GY611 gyro is an AVCS (Angular Vector Control System) rate gyro developed for model helicopter competition.

GY611 Features:
Super narrow pulse (760 micro sec) drive system substantially improves servo response.
Microcomputer high-speed arithmetic processing substantially improves gyro response.
High resolution 12-bit A/D accurately converts the sensor output to a digital signal.
Newest SMM (Silicon Micro Machine) and low-back aeroform case improve vibration resistance and neutral characteristic.
Amp mounts an LCD that allows accurate data setting.

BLS251 servo
High performance digital brushless rudder servo for high performance helicopters. Compatible with: CGY750, GY701, GY520, GY611 and GY601 gyros.
Size: 40 x 20 x 36.8 mm
Weight: 61 g
Power: 3.8 kg/cm vid 4.8V
Speed: 0.06 s/60gr vid 4.8V