No Gunsmithing Required; Increases Mag Tube Capacity
All-steel extension tubes attach directly to the end of the magazine tube and increase capacity by as much as five rounds. Extension cap is machined from solid steel and welded to seamless steel tubing for extra strength. Includes extended magazine spring. Barrel clamps are available separately.
Big Book Catalog, Issue:69, Page:200
SPECS: Steel, blue, matte finish. 12 gauge only. Rounds (RDS) indicates number of rounds extension adds to factory magazine capacity model.