Carlson's Choke Tubes CZ 612 Magazine Extension 8 Shot Black. This Shotgun Magazine Extension from Carlson's Choke Tubes adds 8 extra rounds of 7 shot or 12 extra shots in 12-gauge shotguns. The Carlson's Choke Tubes CZ 612 Magazine Extension 8 Shot fits CZ 612 shotguns only and works with 6-gauge shotguns. This Carlson's Choke Tubes CZ 612 Shotgun Magazine Extension 8 Shot is made using incredibly durable materials that ensure a long lasting and durable addition to your weapon. For a high quality way to boost the caliber of your shotgun choose the Carlson's Choke Tubes CZ 612 Magazine Extension 8 Shot. Specifications for Carlson's Choke Tubes CZ 612 Magazine Extension 8 Shot: Manufacturer: Carlson's Choke Tubes Color: Black Magazine Capacity: 8 Round Condition: New Country of Origin: USA Features of Carlson's Choke Tubes CZ 612 Magazine Extension 8 Shot: CZ 612 (612 Only) Magazine Extension 8 Shot Package Contents: Carlson's Choke Tubes CZ 612 Magazine Extension 8 Shot barrel clamp plus & spring Carlson's Choke Tubes 04511: CZ 612 (612 Only) Magazine Extension 8 Shot Black