Carlson's Choke Tubes 04521 Magazine Extension 12 Gauge Remington 870 Remington 11-87 Remington 1100 Remington Versa Max Remington V3 12 Blued SteelAdd firepower to your favorite shotgun. These magazine extensions are 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