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.
Nordic Components MXT Magazine Extension Nut, Combines with MXT Tubes to Form Complete Extension Kit, Compatible with Beretta 1301, Xtrema, Xtrema2, A400 (Extreme Only), CZ 712/912, Weatherby SA-08 NUT-BR-12-00