The 18-inch genuine, factory brand Remington Model 870 12-Gauge Magazine Extension Kit increases mag tube capacity by two extra rounds. Dependable, factory made magazine extensions provide additional round capacity for tactical operations and competition. All-steel extension tubes attach directly to the end of the magazine tube. Included magazine clamp attaches around the barrel and the extension for added support. Magazine spring is formed from high strength music wire that resists "set" and won't weaken over time.