Holds an additional 2 – 2 ¾ inch shotgun shells. Constructed of Military Type III anodized, 6061 T6 aluminum. Virtually indestructible. Minimum barrel length of 18.5 inches for 7 shot extension. Includes magazine spring. Easy installation. Ratchet base for tight fit. New fluted design. Includes mag extension stand-off cap. Outside diameter of the extension is engineered to match the diameter of the shotgun barrel lug. Manufactured in the USA.