a fucking barrel nut. The handguard has the barrel nut integrated so I have all these parts now I can't put on. so now I gotta wait till friday or sat when its delivered cause the only fucker in my town who has one wouldn't let me come and get it so he lost all my business. And he was the guy who I was going to get my silencer from so he lost alot of business from me, he didn't know how much business he lost by fucking up like he did. Oly 9mm upper troy 10in hand guard gg&g vert grip g27 pistol grip ace skeleton entry stock with 1in pad for stock and a2 stock extension burris red dot hk diopter style buis tlr2 on the hand guard with a led flashlight and lazer sight.