The lower parts are made by various military contractors, for example the fire control parts, AR-15 Disconnector, mag catch, detents, and pins are made by the same contractors that Colt use.  Bolt catches and selectors are made by the same contractor that supplies BM.  They are made to military specs other than the AR dimensions ( not M-16 ) on the fire control parts.  The fire control parts for the M-16 rifle come from the same manufacturer as made for the M-16 rifle in use with the U.S. Military.  Everything is first rate parts, not seconds, and made in the U.S.A.