Dont if your not 100% sure what your doing dont go in a kwa gear box. I cant tell you how many people ask me to fix their kwa only to give me a gearbox completely torn down. And I dont charge a lot but stuff like that pisses me off. Things to consider if your looking for 400fps with .25 your gunna have to replace the spring. Since the kwa doesnt come with a ported piston I would also upgrade that as well. Kwa springs that are in their guns are always under powered one spring down IMO. Some people think they add a 6.01 they will be at 400fps with .25s are tards you need a spring and upgrading for the sake of upgrading youll understand when your paying someone 40-50 bucks just to open the gear box to put a 10-15 dollar spring why you might as well just toss a piston head in there for better compression
