This is a Nickel-Plated Xythos cylinder RETENTION PIN that screws into the Xythos pinfire gun. This is not for the “Big/Female Barrel” Xythos/Xythos-style revolvers where cylinder alignment pin does not completely unscrew. This IS FOR the “Smaller/Male Barrel” Xythos/Xythos-Style revolvers designed with a Screw-In Pin to Hold the Cylinders in place (unscrewed to load/unload) onto the gun base.