-6.03 TBB barrel
That's all the upgrades for now.
Overall, I would give this gun a 10/10 based on sturdiness, externals, weight, and overall functionality.
One of the great things about this gun is the tools needed to do minor things on it are built into the gun, without getting in the way. The upper receiver is very sturdy metal while the lower receiver/stock is made of high quality ABS plastic. The realistic trades from FN Herstal on the side add a very nice touch of realism to it.