This is a Nordic Components Shotgun Magazine Tube Components known as the Mossberg, model BCL-12-MB.
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.
Features:
Threaded Hole to Accept Accessories
Provides Extra Rigidity
Designed for Heavy-Walled Barrels
