Carlson's Choke Tubes 04521 Shotgun Magazine Extension made of Steel with Blued Finsh & Adds 12 Extra Shots for Remington 12 Gauge 870, 1100, 11-87, Versa Max, V3 Add 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 great for home protection, competition shooting, and law enforcement.