The Echo 1 E90 is astounding. The plastic body is extremely durable. The magazine click's solidly into place. The selector switch is sturdy and decisive. The upper receiver as well as the rails are made of metal so that the holo sights and or flashlights mounted on it are secure. The barrel features a 14mm CC threading to accept different  barrel extensions. It also comes with a very solid 7mm metal bushing gearbox.