i think the picture gram ones are aero.
for a while some oly lowers were made by mega--
and where is R-guns and delaware, saber --and a bunch of other makes no the chart?
i have built a bunch of ar-15s in the last few years and to be honest if i had to pick my favorite lower it would be that TNW billet.
those DS arms blems i got last year for $60 were outstanding other than a couple pins being a little tight--LOL
a functional lower for $60-$65?? hell it don't get no better than that.
mall-ninjas may quibble about who made what , who forged this or that. but i have yet to find one that don't work well.
DPMS, doublestar LAR, mega, DS arms, any CMT plus about any lower you can get should build fine--that is the meaning of 'modular"!--LOL!