This is a Mission First Tactical Grip known as the Magwall, model RMG.
The React Magwell Grip is a compact textured vertical grip designed for close handhold application at the low ready or CQB situations. Locates support hand forward of the magazine well to prevent injury if an overcharged round causes the ejection of the magazine. Right and left handed pressure pad wells for wired switches and spare battery storage compartment. Allows the support hand to apply rearward pressure keeping the weapon shouldered" yielding better muzzle control and accuracy.
Features:
Black finish
Designed for M16/M4/AR15/HK416
Secure watertight storage compartment
Will not interfere with magazine