This airsoft hop up by Bullgear is a well-constructed CNC aluminum construction hop up unit made for the Cybergun FN Licensed M249 'Featherweight' AEG. all metal parts In this Hop up unit are entirely manufactured by CNC process giving it a high-quality look. The Hop dial on this unit allows for easy smooth precise adjustments compared to the stock one that has limited adjustment. Also, this hop up unit can use standard hop up rubbers and rollers, making it a must-by accessory for your Cybergun FN M249 'Featherweight' AEG.