Fits Remington and Winchester. Increase magazine capacity to 7 or 8 rounds. Made of virtually indestructible, glass-filled nylon injection molded over a steel connecting nut. Will not rust or dent. New spring and instructions. Note: Must Not extend past end of Barrel. 7 Shot for 18 1/2" barrels; 8 Shot for 20" barrels. 7 Shot Ext., Rem 870/1100/1187