THIS KIT IS WHAT YOU NEED TO BUILD AN AR-15 EXCEPT A STRIPPED LOWER. The receiver is a flat top M4 Mil-Spec upper receiver are forged CNC Machined from 7075-T6 Aluminum, the hardest and most durable material of any upper! This 16" 5.56 Nato Barrel is made from 4150 Chrome Moly steel, and has 1:8 twist rate. The rail is a 15" M-LOK rail made from Airplane Aluminum and then hard coat anodized to improve the strength! **BCG NOT INCLUDED** Barrel: 16" 5.56 Nato Melonite Barrel