Choate Tool Remington 870/1100 Lightweight 20 Gauge 10 Shot Extension +5 rounds, CMT-01-04-35

These kits are constructed of solid blued steel and come with 1 Magazine Extension 678 9 or 10 shot 1 Base Clamp 1 High Visibility Shell Follower. For guns made before about 1987 you might have a 20ga gun made on a 12ga receiver.