The Nordic Components heavy-walled shotgun barrel clamp provides extra rigidity for your magazine extension on shotguns with heavy/overbored barrels or large barrel-to-magazine offset” such as the Mossberg 590/590A1″ 835″ 935″ 930SPX” and the Benelli Nova/Supernova. Each clamp half has a centrally-located 10-32 threaded hole to accept accessories” such as a sling stud” barrel clamp tac rail or QD sling mount.