Great grip upgrade for decent price - FAB Defense Rubberized Pistol Grip for M16/M4/AR-15

I like this is grip a lot. Its very ergonomic and the rubberization makes it very comfortable in the hand and easy to keep a good grip even with sweaty hands. The top part where it joins to the receiver does get narrower than the rest which some may not like, but with a heavier rifle I don't mind it. I haven't had any issues with the door for the compartment not staying shut, if anything its kind of hard to open, but using the nose of a round should help and that's definitely better than it opening too easily (i dont really put anything in there anyway, and in that case it looks like you could take the door off by using a punch to push out the hinge pin).