MAKO/FAB DEFENSE Survival Buttstock with Built-In 10 Rd Magazine Carrier (GL-MAG)

I put one of these on the first AR I built--between LOP and body shape issues you can't make a rifle-stock fit me, but the weight on this helps balance a 16" front end a little better (does it even better with their MBA monopod added on the rear), and the 10-round mag in it gives an option to carry a separate mag of heavier "penetrator" ammo like Mk 262 if your basic load isn't doing the job. Or you can use it to keep a spare full-size magazine ready; I've tried it with both Mission First Tactical and Magpul Gen 2 Pmags and both lock into the carrier just fine. Only complaint is, I wish they'd designed it to use a standard AR mag catch to hold the mag in rather than a proprietary part, because the magazine release is not very compatible with left-handed shooters without coming up with some improvised techniques. If I were building my "Briefcase Special" Mk 18 variant as an SBR rather than a pistol, I'd pick up another of these to throw onto its rear end.