Most Mossberg shotguns come with screw-in choke tubes but many shooters like to add to the standard tubes or need replacements. That's why Mossberg offers such a wide selection from skeet to turkey tubes. Accu-Choke and Accu-Mag choke tubes handle lead steel and all other non-toxic loads. Accu-Choke Tube - Full 20 Ga. For Use with Models 500 505