a barrel, if you can find one. Drill a hole in the grip to make it easier to change the firing speed. Nitro. Electronic feeder.
Good gun. Straight out of the box, shoots fairly straight. Very easy to field strip. never got 11bps like it said until I put on the electronic hopper. Don't use cheap paint or you'll be chopping them up. Overall very satisfied with the speed. Hair trigger, so be careful.
Better barrel is hard to find.
Need to do something with the air flux
Overall this marker, I was very satisfied with. If you want to go full auto then fork out the bucks for a better hopper. My friends that have used it like it very much and for what I paid for it, it was well worth the money.