For enhanced stability in supported/bench-rest/prone shooting positions, you go with a bipod. For enhanced maneuverability of your gun, you go with a vertical forward grip. Using both at the same time is often bulky and heavy. What would happen if you combined both into one item?
Welcome to the Grip Pod: a spring-loaded deployable bipod disguised as an elongated vertical grip. At the push of a button, the vertical grip releases the spring loaded bipod. In order to fold the Grip Pod up, all you have to do is press the two legs together and then insert the whole assembly back into the vertical grip.
Real-deal military versions feature metal inserts in the legs of the Grip Pod, though there is a real LE (law-enforcement) version that features fully-polymer legs. As far as I’ve seen, all Airsoft clones of the Grip Pod are clones of the LE version – they all have polymer legs. I’m currently using an ARES clone of the Grip Pod on my WE M4 GBBR. I like the versatility of the Grip Pod, as my current set up is a clone of a M4A1 with SOPMOD Block I/ Block II kit on it; the Grip Pod allows me to point my carbine and helps to mitigate the (slight) muzzle flip when I’m dumping rounds downrange.
Though the Grip Pod itself isn’t part of the issued SOPMOD stuff, it is still quite common to see real operators use these as personal buys. (Hurray, it works with my MARSOC impression!)