Military Type III Anodized, 6061 T6 aluminum. Place rails at 45 degree angles around the circumference of the forend. Slide rails into any position on the forend for nearly unlimited customization. New slotted barrel nut constructed of Military Type III Anodized, 6061 T6 aluminum. Three set screws locks the forend into Place on the slotted barrel nut. Eliminates the need for the jam nut. Allows forend to be installed flush to the receiver. Manufactured in the USA. Note: Do not over torque the barrel nut during installation. Any damage due to over tightening or applying excessive torque to the barrel nut is not covered under ATI&#146s Limited Lifetime Warranty.