Carlson's Choke Tubes Shotgun Magazine Extension Assembly Benelli M4 12 Gauge 7-Round Grey. These magazine extensions are constructed of blued solid steel and come with spring base clamp with swivel stud (included) to work with quick detachable swivel (not included) and a high visibility follower. The threaded tube replaces you magazine cap and gives you the ability to add extra rounds to you magazine. Easy to follow instructions are included. The magazine extension tube is great for home protection competition shooting and law enforcement. See chart below for the make/model and the magazine capacity. Overall Length of Extensions: 04500 (8.25-inch) 04501 (10.5-inch) 04502 (6.25-inch) 04503 (6.375-inch) 04504 (14.25-inch) 04505 (8.25-inch) 04506 (6.25-inch) 04507 (8.25-inch) 04508 (5-inch) 04510 (13.88) and 04511 (8.5-inch) 04512 (8.38-inch) 04513 (8.13-inch) 04514 (14.13-inch) 04515 (8.13-inch) 04516 (14.13-inch) 04517 (8.5-inch) 04518 (14.25-inch) Magazine round count is for the total capacity using 2 3/4-inch shells including 1 in the chamber when using 3" shells you lose 1 shell capacity. When using 3 1/2" shells you lose 2 shell capacity. Example: 8 shot extension= is 7 (2.75" shells) in the extension and 1 in the chamber 6 (3" shells) in the extension and 1 in the chamber or 5 (3 1/2" shells) in the extension and one in the chamber. Remington extensions require removal of tabs / detent in magazine tube on newer model shotguns All extensions are 12 gauge only. Specifications for Carlson's Choke Tubes Benelli M4 7- Shot Magazine Extension: Manufacturer: Carlson's Choke Tubes Color: Grey Finish: Blued Fabric/Material: Steel Magazine Capacity: 7 Round Gun Make: Benelli Gun Model: Benelli M4 Condition: New Country of Origin: USA Features of Carlson's Choke Tubes Benelli M4 7- Shot Magazine Extension: Benelli M4 7 Shot Magazine Extension Package Contents: Carlson's Choke Tubes Benelli M4 7- Shot Magazine Extension spring What firearm models does the manufacturer say Carlson's Choke Tubes Benelli M4 7- Shot Magazine Extension is compatible with? The manufacturer suggests that Carlson's Choke Tubes Benelli M4 7- Shot Magazine Extension is compatible with Benelli M4Carlson's Choke Tubes 04508: Shotgun Magazine Extension Assembly Benelli M4 12 Gauge 7-Round Grey