I have had this gun for quite some time and I must say I am impressed. Out of the box it is full metal (except the normal polymer parts) but is extremely light which I love. The flashider is very cheap plastic and the ugliest color of orange but is easy enough to get off with some boiling water. It is a bit finicky with mags and the hop up mine came with lost the nub (could be due in part to my amateur barrel change) but when you find a good mag works great. Almost no wobble on the gun at all except when the castle nut comes loose on the stock which requires no effort at all. The only really annoying thing externaly is the extremely limited battery space. Get a peq box or something and save yourself the trouble of wiring it in.
Internally there is a G&P m120 high speed motor (great if you want to leave it all stock), standard G&P gears (my only problem with these is there are only 2 anti reversal notches), a G&P white piston (one of the best for the money), standard brass cylinder polymer piston head and metal spring guide, and a so called m120 spring that cronos more at like 450 (if you want the highest fps stock m4 here you go), and the best of all, it comes with high speed bearings, a must have for high speed lovers like myself. the gearbox shell, piston, and bearings are about the only things left in it now (the rest didn't break i have just upgraded them) and have been holding up great in a build pushing 30 rps.
Overall if you are looking for a great all around gun with great compatibility here you go, plus it's all magpul!
great stock rof
just a great gun
shoots way hot for any indoor fields 450+ fps
cheap flash hider
Other than that a great gun I would 100% recommend