AR-15 / AR-9 / AR-45 Milspec Stripped Upper Receiver -Made out of 7075 T6 Billet Aluminum -Made specifically for pistol caliber builds e.g. 9mm, 40 S&W, 45 ACP, 10mm, etc. -DO NOT USE for rifle calibers e.g. 223/5.56, 300 Blackout, 7.62x39, 350 Legend, etc. -Type III hardcoat Anodized Black -Made in the USA