If the back end of the tube is flat, it's mil-spec. (Stags are.) Angled, is commercial.
I just got in my Stag "group buy" M4 kit and, while every thing else is great, the 6 pos stock has to go. For mil-spec, you'd think they'd get the tolerance down a bit better. Once you get used to a CTR stock, mil or comm, all others suck, unless you electo tape them into quietness.....
I haven't tried their MOE stocks out yet, but if they are tighter, they might save you some bucks for the poser look. I've wondered if I could submerge my rattling CAR stocks in boiling water with vise grips around them to tighten them up a bit, but the CTR makes it a waste of time. I've got three and looking to get another for my Stag.
I want a battle rifle, not a rattle rifle...