This Tri Rail Barrel Mount is made of aluminum and anodized black. It clamps around the barrel and adds a tri rail. It includes a spacer to fit a variety of barrel diameters. This is a perfect addition to the end of an AR-15 with a Front Sight Base. It is also great for an LR-300 Build. Here is a full guide - https://taskernetwork.com/xmod-folding-with-style-the-law-300/