From the moment I laid eyes on it, this was the forestock for me. The most damn awesome thing you could EVER get for your gun. This version is the "firearm only" version, which means there's a piece of metal on the inside that you need to remove in order to put a battery in it. I was able to put a tenergy 9.6v nunchuck battery with little modification. Also, the way I removed it (the metal piece), is by hammering the pegs with a sharp screw driver, so that they break (they have to actual use, even for aesthetics); its all on the internal of it. Anyway, the stock is super sturdy, and fits nice and tight. Its also very comfortable to hold, and looks so very nice on an M4.
Did I say awesome?
can fit a 9.6v, probably up to 10.8v
Very sturdy, tried to break it with my bare hands, and it didn't do a thing (P.S. I'm not this super strong or older, I'm 17, but uh, yeah, this wouldn't break)
Requires very quick and easy modification if you want to put a battery in it.