Chrome Plastic Long Base.. (Rectangular) For Gazelle By Classic Motor Carriages and SSK By Fiberfab.
Base measures 6 3/8" Long, 1 1/8" Wide, Including the Gasket. Distance between screws can vary, mounting plate is slotted.
If there is any trouble adjusting the mirror to your desired position, gently pull the mirror and black gasket out of the housing and loosen the nut hidden under the mirror glass. (see picture below).