Most Mossberg shotguns come with screw-in choke tubes, but many shooters like to add to the standard tubes or need replacements. Mossberg offers such a wide selection from skeet to turkey tubes. Accu-Mag choke tubes handle lead, steel and all other non-toxic loads. Each choke tube is marked with a shot patterning designation as a guide. Patterns can vary depending on ammunition brand, load, and shot size.