21 mm Weaver Picatinny Rail Adapter for Shotgun Red Dot Sight Mount

Our Take

A Weaver adapter for shotguns — 21 mm base width per the title, with a rail surface on top for a red dot. If your shotgun’s rail is the 21 mm Weaver pattern, this is the bridge piece that makes a standard dot mount fit. 40 x 20 mm, about 106 g. The catch, as always, is measurement: ‘Weaver’ and ‘Picatinny’ get used interchangeably in listings and they are not the same slot spacing, so a mismatched pair will wobble or refuse to seat. Measure your shotgun’s rail width before ordering and you’ll know in ten seconds whether this is your part.