Nordic Components MXT Magazine Extension Nut, Combines with MXT Tubes to Form Complete Extension Kit, Compatible with Benelli M1/M2/SBE/SBE2 (Nova/SuperNova use NUT-BR-12-00) NUT-BN-12-00 The MXT extension nut allows for installation of a Nordic Components MXT 12ga shotgun extension tube kit. The nut replaces the factory magazine cap and is required for installation of the extension tube kit.