1-Preban Colt AR15a2, Sporter II, with large(.3125") front pivot pin. The Les Baer flat top upper receiver also uses the large front pin so no adapters needed with this setup. Lower is not blocked, has milspec FCG. Upper receiver has been fitted to the lower and is a very good snug fit. Color of lower and upper match well. Perfect for your M4gery project. $925.00 shipped to your favorite FFL. Please make note this unit does NOT include barrel, carrier, bolt, CH, or buffer assembly.