The Sig Sauer MCX Stock Adapter Kit gives you the ability to upgrade your rifle and install MCX folding stock assemblies (Note: This will not work with Collapsible stocks / braces). CAUTION: Many States and localities regulate the use and/or possession of collapsible and folding stocks. Use, or possession of this product in conjunction with certain other parts, may be illegal in some jurisdictions. It is YOUR responsibility to insure your use of this product is in compliance with all Federal, State and local laws and regulations.