I was at a gun show today, and saw some AR-15 upper barrel/handgurads that I had never seen before. They were on 20" barrels and were a quad rail style. The air cooling holes were a six-sided hex design arranged in a one-two-one-two-one-two... pattern down the length of the handguard. I did not see any manufactures ID on them. The seller didn't understand my question on who made them, and would not let me take a picture of them. Anyone know which ones I am talking about?