"Build is solid, but the case itself is massive. It's longer than the rail on my M4, and it just looks bad. It functions well, but it doesn't come with a hex key, and the hex key I used (proper size, I might add) stripped the screw, so now it's stuck off of my rifle forever.
But, I might add, if I had gotten the hex screw to come off, this would have made a nice attachment for those who don't care about appearances. If your weapon's battery is placed in the barrel (like in an M4), then you can mount the battery outside of the weapon, and in a pinch, you can swap batteries as easily as a magazine. There is even a slot for the wires to come out, obviously for the function.
Pros: Solid build
Makes swapping batteries incredibly easy and fast.
Cons: Hex screw is crap
Box is the size of a tank
Again, if you want your gun to look cool, don't bother with this. If you want functionality, this is probably one of the best upgrades you can make."