Abstract: Two types of choke assemblies are provided to enable a shotgun of specific gauge to be modified in the field to receive a shotgun shell of smaller gauge and also to provide a choke of desired characteristics to suit the needs of the shooter, as for skeet or trap shooting or hunting. Each choke assembly comprises an aluminum tube insertable into the breech end of the shotgun barrel and has integral external bosses to ensure a snug fit. The breech end of the tube is chambered to receive a shotgun shell and the muzzle end of the tube is internally threaded. In one type of choke assembly, a choke is screwed and glued in the threaded tube end at the factory and the entire assembly is installed in the shotgun in the field. Thus, with a plurality of tubes of the same gauge, each would have a different choke permanently attached.