These tubes are 1/4" in diameter. They will not fit your 556 and 223 calibers. Better than oil - hands-down! These Tube Strips are perfect for protection for gun barrels, rifle barrels or lengths of stored metal pipe. Tubes can be cut to length and is a narrow width (.250″ diameter) to fit any ferrous metal tubes and pipes. Just put the Strip into the interior of the metal tube, pipe, or barrel, and cap the ends. The air inside the pipe will be filled with VCI formula that will dissipate when you uncap the ends. Zerust never leaves a residue, is non-toxic, and protects for up to 5 years.