The RE-1 is VLTOR's mil-spec carbine receiver extension tube. The RE-1 features five stock positions" each of which has a corresponding numeral lasered on the top side of the tube for quick visual indexing. These tubes are made from extremely tough 7075-T6 impact extrusions" and feature a mil-spec hardcoat anodized finish (MIL-A-8625 Type III" Class 2). These tubes have a precision-machined internal bore for smooth operation and movement of your buffer components. The receiver extension tube is an important part of your build" and VLTOR realizes this. All of the materials and manufacturing methods for our tubes are optimized to give you the strongest and smoothest functioning tube possible.