Carlson's Choke Tubes 04510 Magazine Extension 12 Gauge Benelli Nova Benelli Super Nova CZ 712 CZ 912 Beretta Extrema 10 Blued SteelAdd firepower to your favorite shotgun. This magazine extension is constructed of blued solid steel and come with spring, base clamp with swivel stud (included) to work with quick detachable swivel (not included) and a high visibility follower (some extensions require factory follower and will not come with one). The threaded tube replaces you magazine cap and gives you the ability to add extra rounds to you magazine. The magazine extension tube is