This chrome plinth allows the stainless flag mirrors (GAM0258/9 flat and GAM0217/8 convex), to attach to the door at the proper angle for good rear vision. This part is not included with the mirror and one is required per mirror. Drill spacing is about 55mm. Sold each.
Note that Mk1-2 door skins must be drilled to accept this plinth, and we recommend a steel plate be used behind the door skin to distribute the weight of the mirror. On Minis from 1970-80, many were already fitted with this part, so they are not needed if already in place. For 1980-on cars, use M90999 and M90997 adapters instead of this part.