As far as I know, G&G mechboxes are standard V2 and any other should fit. However, It's sort of overkill throwing a $250 mechbox into that gun. I'd suggest if you don't know what you're going, get a set of Modify smooth modular gears, a new Modify piston, and you should be up and running agian in no time.
And even if you get a Systema mechbox, their pistons blow donkey cock and need to be replaced.
__________________
|