AR Stoner are made by ASC on the old Cproducts machines. Aside from the controversial change in ownership, they work ok. They make mags for the 6.8, and work for that as reported on TOS.
D&H and quite a few others make mags, too, but the major buying emphasis these days from military contracts is the Pmag. The Marines use them pretty exclusively overseas, and the Brits are receiving the last of a one million unit order. That's the professional recommendation.