The Systema Metal Hop-up Unit, is one of the best. The material it is made of is very good, the edges are smooth, and precise. Fits very VERY nicely into my G&G Gr-16 Commando. I am proud to say i have this hop-up, because it provides, GREAT range, i can hit a torso sized target at 180feet with almost every bb in a 4 shot burst. I love it! Use this and the Systema Bucking and you have a very accurate gun. But!! The turn wheels could be much better! The last wheel that pushes down the nub lever, does not have a stopping point! So i replaced all the wheels with the stock G&G Hop-up wheels.
makes great air seal
bumps up accuracy, range and fps
Bad turn wheel
bad springs(too hard)
Rating: [4 of 5 Stars!]