Precision machined from ordnance grade metal and created to interface in near tolerance with the aluminum stock chassis. Some rocket surgeon drilled and tapped this usually-pristine stainless Mini-fourteen for an aftermarket scope mount. I had been thrilled. I filled the holes with stubby minimal Allen screws and saved about $400. https://andresqdmvd.snack-blog.com/31628546/helping-the-others-realize-the-advantages-of-magpul-stock-shotgun