The Gun Boss pull-through system cleans and protects firearms by pulling fouling out of the muzzle” rather than back into the chamber and action. It comes in a compact” weather-resistant” molded case. Non-marring aluminum connectors and adapters” phosphor bronze brushes” and coated steel cables protect your bores. Every tool snaps securely into place on the high-quality” oil-resistant tray. Fits .17 – .45 cal.” 20 ga. & 12 ga.