This isn’t a preinstalled adapter but a decreased receiver having an built-in folding mechanism. It works with standard stocks, buffer tubes, and all of that. ↩ ∞ Paul Ruffle December 25, 2017, nine:eleven am I bought a person of these guns a month in the past right after looking at https://knoxcsemn.onzeblog.com/32871053/folding-gun-things-to-know-before-you-buy