This is a Magpul Industries Sling Mount known as the Forward Sling Mount SGA, model MAG493.
The Forward Sling Mount is a sling attachment point for the Mossberg 590A1 series of shotguns which clamps onto the barrel and magazine tube. Designed specifically for the A1's heavy walled barrels" it can be configured for use with either Push-Button QD Sling Swivels or one-point clip-in style attachments such as the MS3 Paraclip(TM)" the HK(R) hook" ITW(TM) MASH hook" and others. Made from precision cast steel that is Melonite(R) treated for wear and corrosion resistance. Dedicated fit for Mossberg 590A1 models with factory extended magazine tube and will not fit other Mossberg models. Made in U.S.A.
Features:
Sling mount for the Mossberg 590A1 series
Designed specifically for the A1's heavy walled barrels
Melonite treated for wear and corrosion resistance
