This is the Mamba F4M mini flight controller that is used on the many of the 2 and 3 inch quadcopters from Diatone. This runs the STM32F405 MCU and has the ability to run a 4S battery which is incredible for this size of quadcopter. It has a 6-axis, 8Khz MPU6000 vibration tolerant gyro as well as an in-built OSD.
This flight controller measures just 30x30x5.6mm and weighs just 3.5g. It also comes with 4 small, blue rubber vibration dampener balls.