This is what 2A Armament says :
 
 
 
The XANTHOS-lite was developed to give the end user a lightweight solution for the popular “large frame” 308 (LR308/SR-25) pattern of firearms.  The XANTHOS-lite is geared towards the user who want’s quality material, design, and functionality in a large frame build. The XANTHOS-lite shares the common DPMS HIGH standard for rail height, and will accept most accessories on the market. The lightening cuts on the top of the receiver feature a tapered design to give aftermarket rails a seamless look from receiver to rail. Features such as a tensioning screw, and screw in pin for the bolt release are also included. A generous magazine well aids in reloading. The XANTHOS-lite is sold only as a matched set.

Features:

    3-D Machined from U.S.A. Certified 7075-T6 plate aluminum
    Pocketed design reduces weight, and enhances appearance
    Forward assist has been removed from upper to reduce weight
    Bolt release features screw in pin (Included)
    Standard trigger pin sizing (.156)
    Integrated and lightened trigger guard
    Machined T-Markings and logo for a clean appearance
    Tapered charging handle ramp to eliminate unsightly wear marks
    DPMS HIGH standard rail height
    Barrel nut threads:  1  7/16" - 16 UN-3A
    Integrated tensioning screw guaranties a tight fit (included)
    Bead blasted and hard coat anodized black (Type3 class2)
    Weight: (16oz total) Stripped upper and lower combined
    Compatible with most accessories on the market
    Product of the great state of Idaho, MADE IN THE U.S.A.
    SKU (2A-LFRS-1)
 
The Firearm is required to be delivered to an authorized dealer for presentation of the buyers FFL License, for authorized transfer of the firearm.