From Madbull, these are fully licensed Noveske style Aluminium outer barrels. Tough, light and high quality; Madbull makes some of the best outer barrels around and they offer them in a broad variety of lengths. A standard M16 has a 20 inch barrel while the standard M4A1 has a 14.5 inch barrel but the beauty of the M16 family is their ability to modify the length with a lot more options then that.
This 8.5 Inch (228mm) barrel is dubbed the 'Diplomat' barrel as it is an SBR (short barreled rifle) length barrel that can find use in a PDW (Personal Defense Weapon) format. By giving an M4 what is effectively a long pistol barrel, you will reduce its performance by dropping both power and accuracy but at short range it will be a full fledged M4. For a short range agile weapon, you get full M4 performance which is great for indoor areas.
This is a light grey colored barrel with a low profile black gas block and chrome silver gas tube.