This is a GG&G, Inc. known as the Vertical Forend Grip, model GGG-1543.
GG&G's SFG-1 Short Vertical Forend Grip has a low profile ergonomic design without sacrificing functionality and is perfect for keeping CQB style weapons as compact as possible. A vertical grip for the AR-15 and M-16 has become a valued tactical accessory in military" law enforcement and civilian arenas. It provides the operator with several important advantages" from diminishing muzzle climb during burst-fire sequences to simply offering a more comfortable shooting stance.
Features:
Designed for use with mil-spec-1913 rails
Ideal for M4 carbines and breeching shotguns
No tools required for installation or adjustment in the field
