Magpul MIAD Full Grip Kit in Olive Drab OD Green from Tactical City Gun and Knife Supply.

The Magpul Mission Adaptable Grip (MIAD) is a drop in replacement for the pistol grip on the M16/M4/AR15 series of rifles.

It features removable and replaceable front and rear panels for a custom fit over multiple hand sizes.
Grip features improved ergonomics and positive anti-slip texture on both sides and rear back-strap.
Features a removable inner core that allows for storage (3 round plug included). Custom storage of batteries (waterproof) or bolt/firing pin is available with optional cores.
Full Kit includes 3 size back-straps (S,M,L), 4 front-straps including integrated enhanced trigger guard, 3 round core plug, and installation hardware.