Equipped with an LCD screen and joystick you are able to easily scroll through menus and precisely adjust settings for the utmost control over the system. This FCU is also universally compatible with all PolarStar HPA systems including both dual and single-solenoid systems. This latest REV3 model features updated voltage regulators which greatly improve energy efficiency as well as significantly reducing its overall size. Although it is large when compared the Mini FCU, the REV3 FCU is compact enough to fit into a M4’s buffer tube along with a small 300mAh Lipo pack. Another great feature to this FCU is its integral Motor Control Unit (MCU) which allows it to run a box magazine through the MCU port. LCD screen and Joystick for easy and precise adjustments. Compact 2.25″ x 0.9″ footprint. Integral Motor Control Unit (MCU). Compatible with both Dual and Single-Solenoid HPA systems.