For most pumps and autos including Beretta 390. Rear QD base screws into inletted receptacle in stock. Front base has adapter to fit magazine cap. Does not fit Browning 2000, Winchester 1400, Ithaca 37, Savage 30, Sears 21, or Stevens pumps.
Big Book Catalog, Issue:73, Page:252
Big Book Catalog, Issue:73, Page:253