what's the recommended barrel nut for the Aero enhanced free float hand guard I have standard aero upper receiver — 2 Answers

Gen 1, Gen 2, or Quantum use the BARR (BAR?) nut. It's a proprietary nut sold separately from the handguard by Aero for anywhere between $20-35. Why separately? Because it's also sold permanently affixed to some Aero uppers. It was originally designed to be one of the most solid, rigid (and by extension, most accurate) systems on the market. But lots of people wanted to add it to their non-Aero uppers, and not everyone wanted the girth of the Aero handguards, so Aero also sells the barrel nut separately, and makes uppers with normal barrel nut threads. I know this answer is late, but hopefully it helps others out.