This is my first good quality AEG. I started out with a Umarex g36kv. I chose it for the hand guard length and retractable stock. It came with a carry handle with built-in scope, which I later replaced with a flat rail to attach my own optics. I will put a red dot scope later. I gave it a m4 magwell because m4 magazines are easier to deal with. The battery compartment was too small so i rewired it to the rear and into the butt stock magazine pouch. To make sure the wires would not pinch and run freely with the retractable stock, I had to cut out a few areas. All of the internals are stock. The more I play with this gun and learn about internals I will most likely upgrade it later on.