"The Carlson's Shotgun Magazine Extension adds firepower to your standard, factory hunting shotgun, increasing round capacity for tactical and home defense applications. Each magazine extension is constructed of blued steel and comes with a spring, base clamp, and a high visibility shell follower, and comes threaded to replace the shotgun's factory magazine cap. The shell count for each magazine equals the total magazine capacity using 2-3/4"" shells and 1 round in the chamber. Enhances shotgun for tactical and home defense use Constructed of blued steel Includes spring, base clamp, and shell follower Comes threaded to replace factory magazine cap"