AR57 12\" Complete ULT M-LOK Upper, AR57 Mfg, Factory new. Comes with a 12\" lightweight barrel with M-LOK rails. This AR57 Upper Receiver Assembly converts any AR-15 lower to a pistol capable of shooting 5.7x28 ammunition. The unique upper design loads from the top and ejects downward through the AR-15 mag well. The new generation upper has a stronger, lighter, and more streamlined rail; finished with a beautiful ultra-smooth melonite black coating. Comes with one 50-round magazine.