The EXO ONE (XO1) is a patent-pending multi-caliber exoskeleton for the Sig Sauer P320 Fire Control Unit (FCU). In 20 seconds, you can change your 320 pistol into a legal, bigger, more capable pistol with no FFL and no tools. We just saw the first production models at SHOT, it is all very real.

The ergonomics of the XO1 are formidable and well thought out. Form follows function, there is no excess in this design leaving a grim and determined look.