This anodized aluminum extension nut functions as a coupler and allows for the installation of an extension tube in place of the cap.
Some models of Benelli are being shipped with no magazine extension. They have a cap that screws onto the magazine tube and holds the barrel and forend against the receiver.
This extension nut acts as a coupler and allows installation of a factory or DMW extension tube in place of the cap.
Made from anodized aluminum.